diff --git a/apply.c b/apply.c
index c4c9f849b1..3746310cef 100644
--- a/apply.c
+++ b/apply.c
@@ -4772,6 +4772,9 @@ static int apply_option_parse_exclude(const struct option *opt,
 				      const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	add_name_limit(state, arg, 1);
 	return 0;
 }
@@ -4780,6 +4783,9 @@ static int apply_option_parse_include(const struct option *opt,
 				      const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	add_name_limit(state, arg, 0);
 	state->has_include = 1;
 	return 0;
@@ -4790,6 +4796,9 @@ static int apply_option_parse_p(const struct option *opt,
 				int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	state->p_value = atoi(arg);
 	state->p_value_known = 1;
 	return 0;
@@ -4799,6 +4808,9 @@ static int apply_option_parse_space_change(const struct option *opt,
 					   const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_ARG(arg);
+
 	if (unset)
 		state->ws_ignore_action = ignore_ws_none;
 	else
@@ -4810,6 +4822,9 @@ static int apply_option_parse_whitespace(const struct option *opt,
 					 const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	state->whitespace_option = arg;
 	if (parse_whitespace_option(state, arg))
 		return -1;
@@ -4820,6 +4835,9 @@ static int apply_option_parse_directory(const struct option *opt,
 					const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	strbuf_reset(&state->root);
 	strbuf_addstr(&state->root, arg);
 	strbuf_complete(&state->root, '/');
diff --git a/builtin/blame.c b/builtin/blame.c
index a443af9ee9..06a7163ffe 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -732,6 +732,8 @@ static int blame_copy_callback(const struct option *option, const char *arg, int
 {
 	int *opt = option->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	/*
 	 * -C enables copy from removed files;
 	 * -C -C enables copy from existing files, but only
@@ -754,6 +756,8 @@ static int blame_move_callback(const struct option *option, const char *arg, int
 {
 	int *opt = option->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	*opt |= PICKAXE_BLAME_MOVE;
 
 	if (arg)
diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index 0f6b692df6..1cdd357d52 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -595,6 +595,8 @@ static int batch_option_callback(const struct option *opt,
 {
 	struct batch_options *bo = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (bo->enabled) {
 		return error(_("only one batch option may be specified"));
 	}
diff --git a/builtin/checkout-index.c b/builtin/checkout-index.c
index 88b86c8d9f..eb74774cbc 100644
--- a/builtin/checkout-index.c
+++ b/builtin/checkout-index.c
@@ -132,6 +132,8 @@ static const char * const builtin_checkout_index_usage[] = {
 static int option_parse_stage(const struct option *opt,
 			      const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+
 	if (!strcmp(arg, "all")) {
 		to_tempfile = 1;
 		checkout_stage = CHECKOUT_ALL;
diff --git a/builtin/clean.c b/builtin/clean.c
index 8d9a7dc206..bbcdeb2d9e 100644
--- a/builtin/clean.c
+++ b/builtin/clean.c
@@ -140,6 +140,7 @@ static void clean_print_color(enum color_clean ix)
 static int exclude_cb(const struct option *opt, const char *arg, int unset)
 {
 	struct string_list *exclude_list = opt->value;
+	BUG_ON_OPT_NEG(unset);
 	string_list_append(exclude_list, arg);
 	return 0;
 }
diff --git a/builtin/commit.c b/builtin/commit.c
index 4d7754ca43..500f793fa6 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -161,6 +161,9 @@ static int opt_parse_m(const struct option *opt, const char *arg, int unset)
 static int opt_parse_rename_score(const struct option *opt, const char *arg, int unset)
 {
 	const char **value = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	if (arg != NULL && *arg == '=')
 		arg = arg + 1;
 
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 8f7249f2b1..354ed8bdef 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -98,6 +98,8 @@ static int git_fetch_config(const char *k, const char *v, void *cb)
 
 static int parse_refmap_arg(const struct option *opt, const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+
 	/*
 	 * "git fetch --refmap='' origin foo"
 	 * can be used to tell the command not to store anywhere
diff --git a/builtin/grep.c b/builtin/grep.c
index d8508ddf79..33c8b61595 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -712,11 +712,14 @@ static int context_callback(const struct option *opt, const char *arg,
 static int file_callback(const struct option *opt, const char *arg, int unset)
 {
 	struct grep_opt *grep_opt = opt->value;
-	int from_stdin = !strcmp(arg, "-");
+	int from_stdin;
 	FILE *patterns;
 	int lno = 0;
 	struct strbuf sb = STRBUF_INIT;
 
+	BUG_ON_OPT_NEG(unset);
+
+	from_stdin = !strcmp(arg, "-");
 	patterns = from_stdin ? stdin : fopen(arg, "r");
 	if (!patterns)
 		die_errno(_("cannot open '%s'"), arg);
@@ -737,6 +740,8 @@ static int file_callback(const struct option *opt, const char *arg, int unset)
 static int not_callback(const struct option *opt, const char *arg, int unset)
 {
 	struct grep_opt *grep_opt = opt->value;
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	append_grep_pattern(grep_opt, "--not", "command line", 0, GREP_NOT);
 	return 0;
 }
@@ -744,6 +749,8 @@ static int not_callback(const struct option *opt, const char *arg, int unset)
 static int and_callback(const struct option *opt, const char *arg, int unset)
 {
 	struct grep_opt *grep_opt = opt->value;
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	append_grep_pattern(grep_opt, "--and", "command line", 0, GREP_AND);
 	return 0;
 }
@@ -751,6 +758,8 @@ static int and_callback(const struct option *opt, const char *arg, int unset)
 static int open_callback(const struct option *opt, const char *arg, int unset)
 {
 	struct grep_opt *grep_opt = opt->value;
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	append_grep_pattern(grep_opt, "(", "command line", 0, GREP_OPEN_PAREN);
 	return 0;
 }
@@ -758,6 +767,8 @@ static int open_callback(const struct option *opt, const char *arg, int unset)
 static int close_callback(const struct option *opt, const char *arg, int unset)
 {
 	struct grep_opt *grep_opt = opt->value;
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	append_grep_pattern(grep_opt, ")", "command line", 0, GREP_CLOSE_PAREN);
 	return 0;
 }
@@ -766,6 +777,7 @@ static int pattern_callback(const struct option *opt, const char *arg,
 			    int unset)
 {
 	struct grep_opt *grep_opt = opt->value;
+	BUG_ON_OPT_NEG(unset);
 	append_grep_pattern(grep_opt, arg, "-e option", 0, GREP_PATTERN);
 	return 0;
 }
diff --git a/builtin/init-db.c b/builtin/init-db.c
index 12ddda7e7b..41faffd28d 100644
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -451,6 +451,7 @@ static int guess_repository_type(const char *git_dir)
 
 static int shared_callback(const struct option *opt, const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
 	*((int *) opt->value) = (arg) ? git_config_perm("arg", arg) : PERM_GROUP;
 	return 0;
 }
diff --git a/builtin/interpret-trailers.c b/builtin/interpret-trailers.c
index 4b87e0dd2e..8ae40dec47 100644
--- a/builtin/interpret-trailers.c
+++ b/builtin/interpret-trailers.c
@@ -80,6 +80,8 @@ static int parse_opt_parse(const struct option *opt, const char *arg,
 	v->only_trailers = 1;
 	v->only_input = 1;
 	v->unfold = 1;
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	return 0;
 }
 
diff --git a/builtin/log.c b/builtin/log.c
index 41188e723c..9f2d987294 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -107,6 +107,8 @@ static int log_line_range_callback(const struct option *option, const char *arg,
 {
 	struct line_opt_callback_data *data = option->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (!arg)
 		return -1;
 
@@ -1151,6 +1153,8 @@ static int keep_subject = 0;
 
 static int keep_callback(const struct option *opt, const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	((struct rev_info *)opt->value)->total = -1;
 	keep_subject = 1;
 	return 0;
@@ -1161,6 +1165,7 @@ static int subject_prefix = 0;
 static int subject_prefix_callback(const struct option *opt, const char *arg,
 			    int unset)
 {
+	BUG_ON_OPT_NEG(unset);
 	subject_prefix = 1;
 	((struct rev_info *)opt->value)->subject_prefix = arg;
 	return 0;
@@ -1168,6 +1173,8 @@ static int subject_prefix_callback(const struct option *opt, const char *arg,
 
 static int rfc_callback(const struct option *opt, const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	return subject_prefix_callback(opt, "RFC PATCH", unset);
 }
 
@@ -1176,6 +1183,7 @@ static int numbered_cmdline_opt = 0;
 static int numbered_callback(const struct option *opt, const char *arg,
 			     int unset)
 {
+	BUG_ON_OPT_ARG(arg);
 	*(int *)opt->value = numbered_cmdline_opt = unset ? 0 : 1;
 	if (unset)
 		auto_number =  0;
@@ -1185,6 +1193,7 @@ static int numbered_callback(const struct option *opt, const char *arg,
 static int no_numbered_callback(const struct option *opt, const char *arg,
 				int unset)
 {
+	BUG_ON_OPT_NEG(unset);
 	return numbered_callback(opt, arg, 1);
 }
 
@@ -1192,6 +1201,7 @@ static int output_directory_callback(const struct option *opt, const char *arg,
 			      int unset)
 {
 	const char **dir = (const char **)opt->value;
+	BUG_ON_OPT_NEG(unset);
 	if (*dir)
 		die(_("Two output directories?"));
 	*dir = arg;
diff --git a/builtin/ls-files.c b/builtin/ls-files.c
index 2787453eb1..c70a9c7158 100644
--- a/builtin/ls-files.c
+++ b/builtin/ls-files.c
@@ -475,6 +475,8 @@ static int option_parse_exclude(const struct option *opt,
 {
 	struct string_list *exclude_list = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	exc_given = 1;
 	string_list_append(exclude_list, arg);
 
@@ -486,6 +488,8 @@ static int option_parse_exclude_from(const struct option *opt,
 {
 	struct dir_struct *dir = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	exc_given = 1;
 	add_excludes_from_file(dir, arg);
 
@@ -497,6 +501,9 @@ static int option_parse_exclude_standard(const struct option *opt,
 {
 	struct dir_struct *dir = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
+
 	exc_given = 1;
 	setup_standard_excludes(dir);
 
diff --git a/builtin/merge-file.c b/builtin/merge-file.c
index b08803e611..06a2f90c48 100644
--- a/builtin/merge-file.c
+++ b/builtin/merge-file.c
@@ -15,6 +15,8 @@ static int label_cb(const struct option *opt, const char *arg, int unset)
 	static int label_count = 0;
 	const char **names = (const char **)opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (label_count >= 3)
 		return error("too many labels on the command line");
 	names[label_count++] = arg;
diff --git a/builtin/merge.c b/builtin/merge.c
index 4aa6071598..adb0402e84 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -224,6 +224,7 @@ static int option_parse_x(const struct option *opt,
 static int option_parse_n(const struct option *opt,
 			  const char *arg, int unset)
 {
+	BUG_ON_OPT_ARG(arg);
 	show_diffstat = unset;
 	return 0;
 }
diff --git a/builtin/notes.c b/builtin/notes.c
index c05cd004ab..91faa514aa 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -215,6 +215,8 @@ static int parse_msg_arg(const struct option *opt, const char *arg, int unset)
 {
 	struct note_data *d = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	strbuf_grow(&d->buf, strlen(arg) + 2);
 	if (d->buf.len)
 		strbuf_addch(&d->buf, '\n');
@@ -229,6 +231,8 @@ static int parse_file_arg(const struct option *opt, const char *arg, int unset)
 {
 	struct note_data *d = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (d->buf.len)
 		strbuf_addch(&d->buf, '\n');
 	if (!strcmp(arg, "-")) {
@@ -250,6 +254,8 @@ static int parse_reuse_arg(const struct option *opt, const char *arg, int unset)
 	enum object_type type;
 	unsigned long len;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (d->buf.len)
 		strbuf_addch(&d->buf, '\n');
 
@@ -273,6 +279,7 @@ static int parse_reuse_arg(const struct option *opt, const char *arg, int unset)
 static int parse_reedit_arg(const struct option *opt, const char *arg, int unset)
 {
 	struct note_data *d = opt->value;
+	BUG_ON_OPT_NEG(unset);
 	d->use_editor = 1;
 	return parse_reuse_arg(opt, arg, unset);
 }
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 4eac2f997b..6718e62c15 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -3206,6 +3206,9 @@ static int option_parse_index_version(const struct option *opt,
 {
 	char *c;
 	const char *val = arg;
+
+	BUG_ON_OPT_NEG(unset);
+
 	pack_idx_opts.version = strtoul(val, &c, 10);
 	if (pack_idx_opts.version > 2)
 		die(_("unsupported index version %s"), val);
diff --git a/builtin/read-tree.c b/builtin/read-tree.c
index fbbc98e516..183ee8c1e5 100644
--- a/builtin/read-tree.c
+++ b/builtin/read-tree.c
@@ -44,6 +44,7 @@ static const char * const read_tree_usage[] = {
 static int index_output_cb(const struct option *opt, const char *arg,
 				 int unset)
 {
+	BUG_ON_OPT_NEG(unset);
 	set_alternate_index_output(arg);
 	return 0;
 }
@@ -54,6 +55,8 @@ static int exclude_per_directory_cb(const struct option *opt, const char *arg,
 	struct dir_struct *dir;
 	struct unpack_trees_options *opts;
 
+	BUG_ON_OPT_NEG(unset);
+
 	opts = (struct unpack_trees_options *)opt->value;
 
 	if (opts->dir)
diff --git a/builtin/rebase.c b/builtin/rebase.c
index 0ee06aa363..b84568fc4e 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -703,6 +703,9 @@ static int parse_opt_merge(const struct option *opt, const char *arg, int unset)
 {
 	struct rebase_options *opts = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
+
 	if (!is_interactive(opts))
 		opts->type = REBASE_MERGE;
 
@@ -715,6 +718,9 @@ static int parse_opt_interactive(const struct option *opt, const char *arg,
 {
 	struct rebase_options *opts = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
+
 	opts->type = REBASE_INTERACTIVE;
 	opts->flags |= REBASE_INTERACTIVE_EXPLICIT;
 
diff --git a/builtin/show-branch.c b/builtin/show-branch.c
index b1b540f7f6..934e514944 100644
--- a/builtin/show-branch.c
+++ b/builtin/show-branch.c
@@ -604,6 +604,7 @@ static int parse_reflog_param(const struct option *opt, const char *arg,
 {
 	char *ep;
 	const char **base = (const char **)opt->value;
+	BUG_ON_OPT_NEG(unset);
 	if (!arg)
 		arg = "";
 	reflog = strtoul(arg, &ep, 10);
diff --git a/builtin/show-ref.c b/builtin/show-ref.c
index 2f13f1316f..ed888ffa48 100644
--- a/builtin/show-ref.c
+++ b/builtin/show-ref.c
@@ -151,6 +151,7 @@ static int hash_callback(const struct option *opt, const char *arg, int unset)
 static int exclude_existing_callback(const struct option *opt, const char *arg,
 				     int unset)
 {
+	BUG_ON_OPT_NEG(unset);
 	exclude_arg = 1;
 	*(const char **)opt->value = arg;
 	return 0;
diff --git a/builtin/tag.c b/builtin/tag.c
index 6a396a5090..02f6bd1279 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -338,6 +338,8 @@ static int parse_msg_arg(const struct option *opt, const char *arg, int unset)
 {
 	struct msg_arg *msg = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (!arg)
 		return -1;
 	if (msg->buf.len)
diff --git a/builtin/update-index.c b/builtin/update-index.c
index 07c10bcb7d..faa16c61f1 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -790,12 +790,16 @@ static int refresh(struct refresh_params *o, unsigned int flag)
 static int refresh_callback(const struct option *opt,
 				const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	return refresh(opt->value, 0);
 }
 
 static int really_refresh_callback(const struct option *opt,
 				const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	return refresh(opt->value, REFRESH_REALLY);
 }
 
@@ -803,6 +807,7 @@ static int chmod_callback(const struct option *opt,
 				const char *arg, int unset)
 {
 	char *flip = opt->value;
+	BUG_ON_OPT_NEG(unset);
 	if ((arg[0] != '-' && arg[0] != '+') || arg[1] != 'x' || arg[2])
 		return error("option 'chmod' expects \"+x\" or \"-x\"");
 	*flip = arg[0];
@@ -812,6 +817,8 @@ static int chmod_callback(const struct option *opt,
 static int resolve_undo_clear_callback(const struct option *opt,
 				const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	resolve_undo_clear();
 	return 0;
 }
@@ -847,6 +854,8 @@ static int cacheinfo_callback(struct parse_opt_ctx_t *ctx,
 	unsigned int mode;
 	const char *path;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (!parse_new_style_cacheinfo(ctx->argv[1], &mode, &oid, &path)) {
 		if (add_cacheinfo(mode, &oid, path, 0))
 			die("git update-index: --cacheinfo cannot add %s", path);
@@ -869,6 +878,8 @@ static int stdin_cacheinfo_callback(struct parse_opt_ctx_t *ctx,
 {
 	int *nul_term_line = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (ctx->argc != 1)
 		return error("option '%s' must be the last argument", opt->long_name);
 	allow_add = allow_replace = allow_remove = 1;
@@ -881,6 +892,8 @@ static int stdin_callback(struct parse_opt_ctx_t *ctx,
 {
 	int *read_from_stdin = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (ctx->argc != 1)
 		return error("option '%s' must be the last argument", opt->long_name);
 	*read_from_stdin = 1;
@@ -888,11 +901,13 @@ static int stdin_callback(struct parse_opt_ctx_t *ctx,
 }
 
 static int unresolve_callback(struct parse_opt_ctx_t *ctx,
-				const struct option *opt, int flags)
+				const struct option *opt, int unset)
 {
 	int *has_errors = opt->value;
 	const char *prefix = startup_info->prefix;
 
+	BUG_ON_OPT_NEG(unset);
+
 	/* consume remaining arguments. */
 	*has_errors = do_unresolve(ctx->argc, ctx->argv,
 				prefix, prefix ? strlen(prefix) : 0);
@@ -905,11 +920,13 @@ static int unresolve_callback(struct parse_opt_ctx_t *ctx,
 }
 
 static int reupdate_callback(struct parse_opt_ctx_t *ctx,
-				const struct option *opt, int flags)
+				const struct option *opt, int unset)
 {
 	int *has_errors = opt->value;
 	const char *prefix = startup_info->prefix;
 
+	BUG_ON_OPT_NEG(unset);
+
 	/* consume remaining arguments. */
 	setup_work_tree();
 	*has_errors = do_reupdate(ctx->argc, ctx->argv,
diff --git a/parse-options-cb.c b/parse-options-cb.c
index 6a61166b26..8c9edce52f 100644
--- a/parse-options-cb.c
+++ b/parse-options-cb.c
@@ -58,6 +58,8 @@ int parse_opt_verbosity_cb(const struct option *opt, const char *arg,
 {
 	int *target = opt->value;
 
+	BUG_ON_OPT_ARG(arg);
+
 	if (unset)
 		/* --no-quiet, --no-verbose */
 		*target = 0;
@@ -80,6 +82,8 @@ int parse_opt_commits(const struct option *opt, const char *arg, int unset)
 	struct object_id oid;
 	struct commit *commit;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (!arg)
 		return -1;
 	if (get_oid(arg, &oid))
@@ -110,6 +114,9 @@ int parse_opt_object_name(const struct option *opt, const char *arg, int unset)
 int parse_opt_tertiary(const struct option *opt, const char *arg, int unset)
 {
 	int *target = opt->value;
+
+	BUG_ON_OPT_ARG(arg);
+
 	*target = unset ? 2 : 1;
 	return 0;
 }
diff --git a/parse-options.h b/parse-options.h
index c3f2d2eceb..6c4fe2016d 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -191,6 +191,20 @@ extern int opterror(const struct option *opt, const char *reason, int flags);
 #define opterror(o,r,f) (opterror((o),(r),(f)), const_error())
 #endif
 
+/*
+ * Use these assertions for callbacks that expect to be called with NONEG and
+ * NOARG respectively, and do not otherwise handle the "unset" and "arg"
+ * parameters.
+ */
+#define BUG_ON_OPT_NEG(unset) do { \
+	if ((unset)) \
+		BUG("option callback does not expect negation"); \
+} while (0)
+#define BUG_ON_OPT_ARG(arg) do { \
+	if ((arg)) \
+		BUG("option callback does not expect an argument"); \
+} while (0)
+
 /*----- incremental advanced APIs -----*/
 
 enum {
diff --git a/ref-filter.c b/ref-filter.c
index 0c45ed9d94..7eca436223 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -2316,6 +2316,8 @@ int parse_opt_merge_filter(const struct option *opt, const char *arg, int unset)
 	struct object_id oid;
 	int no_merged = starts_with(opt->long_name, "no");
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (rf->merge) {
 		if (no_merged) {
 			return opterror(opt, "is incompatible with --merged", 0);
diff --git a/t/helper/test-parse-options.c b/t/helper/test-parse-options.c
index f0623bb42b..47fee660b8 100644
--- a/t/helper/test-parse-options.c
+++ b/t/helper/test-parse-options.c
@@ -36,6 +36,7 @@ static int length_callback(const struct option *opt, const char *arg, int unset)
 
 static int number_callback(const struct option *opt, const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
 	*(int *)opt->value = strtol(arg, NULL, 10);
 	return 0;
 }