diff --git a/Documentation/git-commit.txt b/Documentation/git-commit.txt
index 3fbb7352bc..f970a43422 100644
--- a/Documentation/git-commit.txt
+++ b/Documentation/git-commit.txt
@@ -145,8 +145,7 @@ OPTIONS
 	If multiple `-m` options are given, their values are
 	concatenated as separate paragraphs.
 +
-The `-m` option is mutually exclusive with `-c`, `-C`, `-F`, and
-`--fixup`.
+The `-m` option is mutually exclusive with `-c`, `-C`, and `-F`.
 
 -t <file>::
 --template=<file>::
diff --git a/builtin/commit.c b/builtin/commit.c
index 8a87701414..4e68394391 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -701,7 +701,7 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 		}
 	}
 
-	if (have_option_m) {
+	if (have_option_m && !fixup_message) {
 		strbuf_addbuf(&sb, &message);
 		hook_arg1 = "message";
 	} else if (logfile && !strcmp(logfile, "-")) {
@@ -731,6 +731,8 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 		ctx.output_encoding = get_commit_output_encoding();
 		format_commit_message(commit, "fixup! %s\n\n",
 				      &sb, &ctx);
+		if (have_option_m)
+			strbuf_addbuf(&sb, &message);
 		hook_arg1 = "message";
 	} else if (!stat(git_path_merge_msg(), &statbuf)) {
 		/*
@@ -1197,8 +1199,8 @@ static int parse_and_validate_options(int argc, const char *argv[],
 		f++;
 	if (f > 1)
 		die(_("Only one of -c/-C/-F/--fixup can be used."));
-	if (have_option_m && f > 0)
-		die((_("Option -m cannot be combined with -c/-C/-F/--fixup.")));
+	if (have_option_m && (edit_message || use_message || logfile))
+		die((_("Option -m cannot be combined with -c/-C/-F.")));
 	if (f || have_option_m)
 		template_file = NULL;
 	if (edit_message)
diff --git a/t/t7500-commit.sh b/t/t7500-commit.sh
index 5739d3ed23..2d95778b74 100755
--- a/t/t7500-commit.sh
+++ b/t/t7500-commit.sh
@@ -272,6 +272,14 @@ test_expect_success 'commit --fixup provides correct one-line commit message' '
 	commit_msg_is "fixup! target message subject line"
 '
 
+test_expect_success 'commit --fixup -m"something" -m"extra"' '
+	commit_for_rebase_autosquash_setup &&
+	git commit --fixup HEAD~1 -m"something" -m"extra" &&
+	commit_msg_is "fixup! target message subject linesomething
+
+extra"
+'
+
 test_expect_success 'commit --squash works with -F' '
 	commit_for_rebase_autosquash_setup &&
 	echo "log message from file" >msgfile &&
@@ -325,7 +333,6 @@ test_expect_success 'invalid message options when using --fixup' '
 	test_must_fail git commit --fixup HEAD~1 --squash HEAD~2 &&
 	test_must_fail git commit --fixup HEAD~1 -C HEAD~2 &&
 	test_must_fail git commit --fixup HEAD~1 -c HEAD~2 &&
-	test_must_fail git commit --fixup HEAD~1 -m "cmdline message" &&
 	test_must_fail git commit --fixup HEAD~1 -F log
 '