diff --git a/builtin/blame.c b/builtin/blame.c
index 1407ae7eb2..4916eb2bd2 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -1551,8 +1551,7 @@ static void assign_blame(struct scoreboard *sb, int opt)
 		 */
 		origin_incref(suspect);
 		commit = suspect->commit;
-		if (!commit->object.parsed)
-			parse_commit(commit);
+		parse_commit(commit);
 		if (reverse ||
 		    (!(commit->object.flags & UNINTERESTING) &&
 		     !(revs->max_age != -1 && commit->date < revs->max_age)))
diff --git a/builtin/branch.c b/builtin/branch.c
index f157f92f48..636a16ea4e 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -502,7 +502,7 @@ static void add_verbose_info(struct strbuf *out, struct ref_item *item,
 	const char *sub = _(" **** invalid ref ****");
 	struct commit *commit = item->commit;
 
-	if (commit && !parse_commit(commit)) {
+	if (!parse_commit(commit)) {
 		pp_commit_easy(CMIT_FMT_ONELINE, commit, &subject);
 		sub = subject.buf;
 	}
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 54f80bd38a..904fd715f0 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -380,8 +380,8 @@ static void show_local_changes(struct object *head,
 static void describe_detached_head(const char *msg, struct commit *commit)
 {
 	struct strbuf sb = STRBUF_INIT;
-	parse_commit(commit);
-	pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
+	if (!parse_commit(commit))
+		pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 	fprintf(stderr, "%s %s... %s\n", msg,
 		find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
 	strbuf_release(&sb);
@@ -677,12 +677,12 @@ static int add_pending_uninteresting_ref(const char *refname,
 
 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 {
-	parse_commit(commit);
 	strbuf_addstr(sb, "  ");
 	strbuf_addstr(sb,
 		find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 	strbuf_addch(sb, ' ');
-	pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
+	if (!parse_commit(commit))
+		pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 	strbuf_addch(sb, '\n');
 }
 
@@ -789,7 +789,7 @@ static int switch_branches(const struct checkout_opts *opts,
 		new->commit = old.commit;
 		if (!new->commit)
 			die(_("You are on a branch yet to be born"));
-		parse_commit(new->commit);
+		parse_commit_or_die(new->commit);
 	}
 
 	ret = merge_working_tree(opts, &old, new, &writeout_error);
@@ -995,7 +995,7 @@ static int parse_branchname_arg(int argc, const char **argv,
 		/* not a commit */
 		*source_tree = parse_tree_indirect(rev);
 	} else {
-		parse_commit(new->commit);
+		parse_commit_or_die(new->commit);
 		*source_tree = new->commit->tree;
 	}
 
diff --git a/builtin/commit.c b/builtin/commit.c
index 6ab4605cf5..e89c519192 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1338,7 +1338,7 @@ static void print_summary(const char *prefix, const unsigned char *sha1,
 	commit = lookup_commit(sha1);
 	if (!commit)
 		die(_("couldn't look up newly created commit"));
-	if (!commit || parse_commit(commit))
+	if (parse_commit(commit))
 		die(_("could not parse newly created commit"));
 
 	strbuf_addstr(&format, "format:%h] %s");
@@ -1525,7 +1525,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		current_head = NULL;
 	else {
 		current_head = lookup_commit_or_die(sha1, "HEAD");
-		if (!current_head || parse_commit(current_head))
+		if (parse_commit(current_head))
 			die(_("could not parse HEAD commit"));
 	}
 	argc = parse_and_validate_options(argc, argv, builtin_commit_options,
diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index 78250eab08..ea6305258d 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -287,7 +287,7 @@ static void handle_commit(struct commit *commit, struct rev_info *rev)
 
 	rev->diffopt.output_format = DIFF_FORMAT_CALLBACK;
 
-	parse_commit(commit);
+	parse_commit_or_die(commit);
 	author = strstr(commit->buffer, "\nauthor ");
 	if (!author)
 		die ("Could not find author in commit %s",
@@ -308,7 +308,7 @@ static void handle_commit(struct commit *commit, struct rev_info *rev)
 	if (commit->parents &&
 	    get_object_mark(&commit->parents->item->object) != 0 &&
 	    !full_tree) {
-		parse_commit(commit->parents->item);
+		parse_commit_or_die(commit->parents->item);
 		diff_tree_sha1(commit->parents->item->tree->object.sha1,
 			       commit->tree->object.sha1, "", &rev->diffopt);
 	}
diff --git a/builtin/name-rev.c b/builtin/name-rev.c
index 20fcf8c696..23daaa7d99 100644
--- a/builtin/name-rev.c
+++ b/builtin/name-rev.c
@@ -27,8 +27,7 @@ static void name_rev(struct commit *commit,
 	struct commit_list *parents;
 	int parent_number = 1;
 
-	if (!commit->object.parsed)
-		parse_commit(commit);
+	parse_commit(commit);
 
 	if (commit->date < cutoff)
 		return;
diff --git a/builtin/show-branch.c b/builtin/show-branch.c
index 001f29ca1b..46902c3de4 100644
--- a/builtin/show-branch.c
+++ b/builtin/show-branch.c
@@ -227,8 +227,7 @@ static void join_revs(struct commit_list **list_p,
 			parents = parents->next;
 			if ((this_flag & flags) == flags)
 				continue;
-			if (!p->object.parsed)
-				parse_commit(p);
+			parse_commit(p);
 			if (mark_seen(p, seen_p) && !still_interesting)
 				extra--;
 			p->object.flags |= flags;
diff --git a/commit.c b/commit.c
index de16a3c0a2..11509ffc47 100644
--- a/commit.c
+++ b/commit.c
@@ -79,7 +79,7 @@ struct commit *lookup_commit_reference_by_name(const char *name)
 	if (get_sha1_committish(name, sha1))
 		return NULL;
 	commit = lookup_commit_reference(sha1);
-	if (!commit || parse_commit(commit))
+	if (parse_commit(commit))
 		return NULL;
 	return commit;
 }
@@ -341,6 +341,13 @@ int parse_commit(struct commit *item)
 	return ret;
 }
 
+void parse_commit_or_die(struct commit *item)
+{
+	if (parse_commit(item))
+		die("unable to parse commit %s",
+		    item ? sha1_to_hex(item->object.sha1) : "(null)");
+}
+
 int find_commit_subject(const char *commit_buffer, const char **subject)
 {
 	const char *eol;
diff --git a/commit.h b/commit.h
index bd841f4d0c..934af889f7 100644
--- a/commit.h
+++ b/commit.h
@@ -49,6 +49,7 @@ struct commit *lookup_commit_or_die(const unsigned char *sha1, const char *ref_n
 
 int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long size);
 int parse_commit(struct commit *item);
+void parse_commit_or_die(struct commit *item);
 
 /* Find beginning and length of commit subject. */
 int find_commit_subject(const char *commit_buffer, const char **subject);
diff --git a/fetch-pack.c b/fetch-pack.c
index 1042448fa0..5a1200f1a0 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -47,9 +47,8 @@ static void rev_list_push(struct commit *commit, int mark)
 	if (!(commit->object.flags & mark)) {
 		commit->object.flags |= mark;
 
-		if (!(commit->object.parsed))
-			if (parse_commit(commit))
-				return;
+		if (parse_commit(commit))
+			return;
 
 		prio_queue_put(&rev_list, commit);
 
@@ -128,8 +127,7 @@ static const unsigned char *get_rev(void)
 			return NULL;
 
 		commit = prio_queue_get(&rev_list);
-		if (!commit->object.parsed)
-			parse_commit(commit);
+		parse_commit(commit);
 		parents = commit->parents;
 
 		commit->object.flags |= POPPED;
diff --git a/log-tree.c b/log-tree.c
index 8534d91826..e958d0748f 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -734,7 +734,7 @@ static int log_tree_diff(struct rev_info *opt, struct commit *commit, struct log
 	if (!opt->diff && !DIFF_OPT_TST(&opt->diffopt, EXIT_WITH_STATUS))
 		return 0;
 
-	parse_commit(commit);
+	parse_commit_or_die(commit);
 	sha1 = commit->tree->object.sha1;
 
 	/* Root commit? */
@@ -759,7 +759,7 @@ static int log_tree_diff(struct rev_info *opt, struct commit *commit, struct log
 			 * parent, showing summary diff of the others
 			 * we merged _in_.
 			 */
-			parse_commit(parents->item);
+			parse_commit_or_die(parents->item);
 			diff_tree_sha1(parents->item->tree->object.sha1,
 				       sha1, "", &opt->diffopt);
 			log_tree_diff_flush(opt);
@@ -774,7 +774,7 @@ static int log_tree_diff(struct rev_info *opt, struct commit *commit, struct log
 	for (;;) {
 		struct commit *parent = parents->item;
 
-		parse_commit(parent);
+		parse_commit_or_die(parent);
 		diff_tree_sha1(parent->tree->object.sha1,
 			       sha1, "", &opt->diffopt);
 		log_tree_diff_flush(opt);
diff --git a/notes-utils.c b/notes-utils.c
index 9107c379d9..7bb3473dbe 100644
--- a/notes-utils.c
+++ b/notes-utils.c
@@ -18,7 +18,7 @@ void create_notes_commit(struct notes_tree *t, struct commit_list *parents,
 		unsigned char parent_sha1[20];
 		if (!read_ref(t->ref, parent_sha1)) {
 			struct commit *parent = lookup_commit(parent_sha1);
-			if (!parent || parse_commit(parent))
+			if (parse_commit(parent))
 				die("Failed to find/parse commit %s", t->ref);
 			commit_list_insert(parent, &parents);
 		}
diff --git a/sha1_name.c b/sha1_name.c
index e9c299943b..2f37488b96 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -581,8 +581,6 @@ static int get_parent(const char *name, int len,
 	if (ret)
 		return ret;
 	commit = lookup_commit_reference(sha1);
-	if (!commit)
-		return -1;
 	if (parse_commit(commit))
 		return -1;
 	if (!idx) {
diff --git a/shallow.c b/shallow.c
index cdf37d694d..961cf6f024 100644
--- a/shallow.c
+++ b/shallow.c
@@ -90,8 +90,7 @@ struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
 				cur_depth = *(int *)commit->util;
 			}
 		}
-		if (parse_commit(commit))
-			die("invalid commit");
+		parse_commit_or_die(commit);
 		cur_depth++;
 		if (cur_depth >= depth) {
 			commit_list_insert(commit, &result);
diff --git a/upload-pack.c b/upload-pack.c
index c989a737f9..d30f339e70 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -649,8 +649,7 @@ static void receive_needs(void)
 				/* make sure the real parents are parsed */
 				unregister_shallow(object->sha1);
 				object->parsed = 0;
-				if (parse_commit((struct commit *)object))
-					die("invalid commit");
+				parse_commit_or_die((struct commit *)object);
 				parents = ((struct commit *)object)->parents;
 				while (parents) {
 					add_object_array(&parents->item->object,