diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index a6903419c4..8bfa5a9272 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -894,7 +894,7 @@ is used.  In that case the suggested commit message is only the message
 of the "fixup -c" commit, and an editor is opened allowing you to edit
 the message.  The contents (patch) of the "fixup -c" commit are still
 incorporated into the folded commit. If there is more than one "fixup -c"
-commit, the message from the last last one is used.  You can also use
+commit, the message from the final one is used.  You can also use
 "fixup -C" to get the same behavior as "fixup -c" except without opening
 an editor.
 
diff --git a/rebase-interactive.c b/rebase-interactive.c
index c3bd02adee..b6cbd16a17 100644
--- a/rebase-interactive.c
+++ b/rebase-interactive.c
@@ -44,9 +44,10 @@ void append_todo_help(int command_count,
 "r, reword <commit> = use commit, but edit the commit message\n"
 "e, edit <commit> = use commit, but stop for amending\n"
 "s, squash <commit> = use commit, but meld into previous commit\n"
-"f, fixup [-C | -c] <commit> = like \"squash\", but discard this\n"
-"                   commit's log message. Use -C to replace with this\n"
-"                   commit message or -c to edit the commit message\n"
+"f, fixup [-C | -c] <commit> = like \"squash\" but keep only the previous\n"
+"                   commit's log message, unless -C is used, in which case\n"
+"                   keep only this commit's message; -c is same as -C but\n"
+"                   opens the editor\n"
 "x, exec <command> = run command (the rest of the line) using shell\n"
 "b, break = stop here (continue rebase later with 'git rebase --continue')\n"
 "d, drop <commit> = remove commit\n"
@@ -55,7 +56,7 @@ void append_todo_help(int command_count,
 "m, merge [-C <commit> | -c <commit>] <label> [# <oneline>]\n"
 ".       create a merge commit using the original merge commit's\n"
 ".       message (or the oneline, if no original merge commit was\n"
-".       specified). Use -c <commit> to reword the commit message.\n"
+".       specified); use -c <commit> to reword the commit message\n"
 "\n"
 "These lines can be re-ordered; they are executed from top to bottom.\n");
 	unsigned edit_todo = !(shortrevisions && shortonto);
diff --git a/sequencer.c b/sequencer.c
index e32020252d..aedca2d52b 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -1752,8 +1752,7 @@ static const char skip_first_commit_msg_str[] = N_("The 1st commit message will
 static const char skip_nth_commit_msg_fmt[] = N_("The commit message #%d will be skipped:");
 static const char combined_commit_msg_fmt[] = N_("This is a combination of %d commits.");
 
-static int check_fixup_flag(enum todo_command command,
-			    enum todo_item_flags flag)
+static int is_fixup_flag(enum todo_command command, unsigned flag)
 {
 	return command == TODO_FIXUP && ((flag & TODO_REPLACE_FIXUP_MSG) ||
 					 (flag & TODO_EDIT_FIXUP_MSG));
@@ -1858,7 +1857,7 @@ static void update_squash_message_for_fixup(struct strbuf *msg)
 
 static int append_squash_message(struct strbuf *buf, const char *body,
 			 enum todo_command command, struct replay_opts *opts,
-			 enum todo_item_flags flag)
+			 unsigned flag)
 {
 	const char *fixup_msg;
 	size_t commented_len = 0, fixup_off;
@@ -1882,7 +1881,7 @@ static int append_squash_message(struct strbuf *buf, const char *body,
 	strbuf_addstr(buf, body + commented_len);
 
 	/* fixup -C after squash behaves like squash */
-	if (check_fixup_flag(command, flag) && !seen_squash(opts)) {
+	if (is_fixup_flag(command, flag) && !seen_squash(opts)) {
 		/*
 		 * We're replacing the commit message so we need to
 		 * append the Signed-off-by: trailer if the user
@@ -1914,7 +1913,7 @@ static int update_squash_messages(struct repository *r,
 				  enum todo_command command,
 				  struct commit *commit,
 				  struct replay_opts *opts,
-				  enum todo_item_flags flag)
+				  unsigned flag)
 {
 	struct strbuf buf = STRBUF_INIT;
 	int res = 0;
@@ -1937,7 +1936,7 @@ static int update_squash_messages(struct repository *r,
 			    opts->current_fixup_count + 2);
 		strbuf_splice(&buf, 0, eol - buf.buf, header.buf, header.len);
 		strbuf_release(&header);
-		if (check_fixup_flag(command, flag) && !seen_squash(opts))
+		if (is_fixup_flag(command, flag) && !seen_squash(opts))
 			update_squash_message_for_fixup(&buf);
 	} else {
 		struct object_id head;
@@ -1960,11 +1959,11 @@ static int update_squash_messages(struct repository *r,
 		strbuf_addf(&buf, "%c ", comment_line_char);
 		strbuf_addf(&buf, _(combined_commit_msg_fmt), 2);
 		strbuf_addf(&buf, "\n%c ", comment_line_char);
-		strbuf_addstr(&buf, check_fixup_flag(command, flag) ?
+		strbuf_addstr(&buf, is_fixup_flag(command, flag) ?
 			      _(skip_first_commit_msg_str) :
 			      _(first_commit_msg_str));
 		strbuf_addstr(&buf, "\n\n");
-		if (check_fixup_flag(command, flag))
+		if (is_fixup_flag(command, flag))
 			strbuf_add_commented_lines(&buf, body, strlen(body));
 		else
 			strbuf_addstr(&buf, body);
@@ -1977,7 +1976,7 @@ static int update_squash_messages(struct repository *r,
 			     oid_to_hex(&commit->object.oid));
 	find_commit_subject(message, &body);
 
-	if (command == TODO_SQUASH || check_fixup_flag(command, flag)) {
+	if (command == TODO_SQUASH || is_fixup_flag(command, flag)) {
 		res = append_squash_message(&buf, body, command, opts, flag);
 	} else if (command == TODO_FIXUP) {
 		strbuf_addf(&buf, "\n%c ", comment_line_char);
@@ -5670,7 +5669,7 @@ static int subject2item_cmp(const void *fndata,
 
 define_commit_slab(commit_todo_item, struct todo_item *);
 
-static inline int skip_fixup_amend_squash(const char *subject, const char **p) {
+static int skip_fixupish(const char *subject, const char **p) {
 	return skip_prefix(subject, "fixup! ", p) ||
 	       skip_prefix(subject, "amend! ", p) ||
 	       skip_prefix(subject, "squash! ", p);
@@ -5734,13 +5733,13 @@ int todo_list_rearrange_squash(struct todo_list *todo_list)
 		format_subject(&buf, subject, " ");
 		subject = subjects[i] = strbuf_detach(&buf, &subject_len);
 		unuse_commit_buffer(item->commit, commit_buffer);
-		if (skip_fixup_amend_squash(subject, &p)) {
+		if (skip_fixupish(subject, &p)) {
 			struct commit *commit2;
 
 			for (;;) {
 				while (isspace(*p))
 					p++;
-				if (!skip_fixup_amend_squash(p, &p))
+				if (!skip_fixupish(p, &p))
 					break;
 			}
 
diff --git a/t/lib-rebase.sh b/t/lib-rebase.sh
index 27928ecb94..dc75b83451 100644
--- a/t/lib-rebase.sh
+++ b/t/lib-rebase.sh
@@ -15,10 +15,11 @@
 #       specified line.
 #
 #   "<cmd> <lineno>" -- add a line with the specified command
-#       ("pick", "squash", "fixup", "edit", "reword" or "drop") and the
-#       SHA1 taken from the specified line.
+#       ("pick", "squash", "fixup"|"fixup_-C"|"fixup_-c", "edit", "reword" or "drop")
+#       and the SHA1 taken from the specified line.
 #
-#   "exec_cmd_with_args" -- add an "exec cmd with args" line.
+#   "_" -- add a space, like "fixup_-C" implies "fixup -C" and
+#       "exec_cmd_with_args" add an "exec cmd with args" line.
 #
 #   "#" -- Add a comment line.
 #
diff --git a/t/t3437-rebase-fixup-options.sh b/t/t3437-rebase-fixup-options.sh
index 945df2555b..a5a20354e3 100755
--- a/t/t3437-rebase-fixup-options.sh
+++ b/t/t3437-rebase-fixup-options.sh
@@ -9,7 +9,9 @@ This test checks the "fixup [-C|-c]" command of rebase interactive.
 In addition to amending the contents of the commit, "fixup -C"
 replaces the original commit message with the message of the fixup
 commit. "fixup -c" also replaces the original message, but opens the
-editor to allow the user to edit the message before committing.
+editor to allow the user to edit the message before committing. Similar
+to the "fixup" command that works with "fixup!", "fixup -C" works with
+"amend!" upon --autosquash.
 '
 
 . ./test-lib.sh
@@ -18,35 +20,35 @@ editor to allow the user to edit the message before committing.
 
 EMPTY=""
 
+# test_commit_message <rev> -m <msg>
+# test_commit_message <rev> <path>
+# Verify that the commit message of <rev> matches
+# <msg> or the content of <path>.
 test_commit_message () {
-	rev="$1" && # commit or tag we want to test
-	file="$2" && # test against the content of a file
-	git show --no-patch --pretty=format:%B "$rev" >actual-message &&
-	if test "$2" = -m
-	then
-		str="$3" && # test against a string
-		printf "%s\n" "$str" >tmp-expected-message &&
-		file="tmp-expected-message"
-	fi
-	test_cmp "$file" actual-message
+	git show --no-patch --pretty=format:%B "$1" >actual &&
+	case "$2" in
+	-m)
+		echo "$3" >expect &&
+		test_cmp expect actual ;;
+	*)
+		test_cmp "$2" actual ;;
+	esac
 }
 
 get_author () {
 	rev="$1" &&
-	git log -1 --pretty=format:"%an %ae" "$rev"
+	git log -1 --pretty=format:"%an %ae %at" "$rev"
 }
 
 test_expect_success 'setup' '
 	cat >message <<-EOF &&
-		amend! B
-		${EMPTY}
-		new subject
-		${EMPTY}
-		new
-		body
-		EOF
-
-	sed "1,2d" message >expected-message &&
+	amend! B
+	$EMPTY
+	new subject
+	$EMPTY
+	new
+	body
+	EOF
 
 	test_commit A A &&
 	test_commit B B &&
@@ -68,40 +70,43 @@ test_expect_success 'setup' '
 	echo B1 >B &&
 	test_tick &&
 	git commit --fixup=HEAD -a &&
+	git tag B1 &&
 	test_tick &&
 	git commit --allow-empty -F - <<-EOF &&
-		amend! B
-		${EMPTY}
-		B
-		${EMPTY}
-		edited 1
-		EOF
+	amend! B
+	$EMPTY
+	B
+	$EMPTY
+	edited 1
+	EOF
 	test_tick &&
 	git commit --allow-empty -F - <<-EOF &&
-		amend! amend! B
-		${EMPTY}
-		B
-		${EMPTY}
-		edited 1
-		${EMPTY}
-		edited 2
-		EOF
+	amend! amend! B
+	$EMPTY
+	B
+	$EMPTY
+	edited 1
+	$EMPTY
+	edited 2
+	EOF
 	echo B2 >B &&
 	test_tick &&
 	FAKE_COMMIT_AMEND="edited squash" git commit --squash=HEAD -a &&
+	git tag B2 &&
 	echo B3 >B &&
 	test_tick &&
 	git commit -a -F - <<-EOF &&
-		amend! amend! amend! B
-		${EMPTY}
-		B
-		${EMPTY}
-		edited 1
-		${EMPTY}
-		edited 2
-		${EMPTY}
-		edited 3
-		EOF
+	amend! amend! amend! B
+	$EMPTY
+	B
+	$EMPTY
+	edited 1
+	$EMPTY
+	edited 2
+	$EMPTY
+	edited 3
+	EOF
+	git tag B3 &&
 
 	GIT_AUTHOR_NAME="Rebase Author" &&
 	GIT_AUTHOR_EMAIL="rebase.author@example.com" &&
@@ -134,6 +139,7 @@ test_expect_success 'simple fixup -c works' '
 test_expect_success 'fixup -C removes amend! from message' '
 	test_when_finished "test_might_fail git rebase --abort" &&
 	git checkout --detach A1 &&
+	git log -1 --pretty=format:%b >expected-message &&
 	FAKE_LINES="1 fixup_-C 2" git rebase -i A &&
 	test_cmp_rev HEAD^ A &&
 	test_cmp_rev HEAD^{tree} A1^{tree} &&
@@ -145,13 +151,14 @@ test_expect_success 'fixup -C removes amend! from message' '
 test_expect_success 'fixup -C with conflicts gives correct message' '
 	test_when_finished "test_might_fail git rebase --abort" &&
 	git checkout --detach A1 &&
+	git log -1 --pretty=format:%b >expected-message &&
+	test_write_lines "" "edited" >>expected-message &&
 	test_must_fail env FAKE_LINES="1 fixup_-C 2" git rebase -i conflicts &&
 	git checkout --theirs -- A &&
 	git add A &&
 	FAKE_COMMIT_AMEND=edited git rebase --continue &&
 	test_cmp_rev HEAD^ conflicts &&
 	test_cmp_rev HEAD^{tree} A1^{tree} &&
-	test_write_lines "" edited >>expected-message &&
 	test_commit_message HEAD expected-message &&
 	get_author HEAD >actual-author &&
 	test_cmp expected-author actual-author
@@ -167,12 +174,12 @@ test_expect_success 'skipping fixup -C after fixup gives correct message' '
 '
 
 test_expect_success 'sequence of fixup, fixup -C & squash --signoff works' '
-	git checkout --detach branch &&
+	git checkout --detach B3 &&
 	FAKE_LINES="1 fixup 2 fixup_-C 3 fixup_-C 4 squash 5 fixup_-C 6" \
 		FAKE_COMMIT_AMEND=squashed \
 		FAKE_MESSAGE_COPY=actual-squash-message \
 		git -c commit.status=false rebase -ik --signoff A &&
-	git diff-tree --exit-code --patch HEAD branch -- &&
+	git diff-tree --exit-code --patch HEAD B3 -- &&
 	test_cmp_rev HEAD^ A &&
 	test_i18ncmp "$TEST_DIRECTORY/t3437/expected-squash-message" \
 		actual-squash-message
@@ -180,7 +187,7 @@ test_expect_success 'sequence of fixup, fixup -C & squash --signoff works' '
 
 test_expect_success 'first fixup -C commented out in sequence fixup fixup -C fixup -C' '
 	test_when_finished "test_might_fail git rebase --abort" &&
-	git checkout branch && git checkout --detach branch~2 &&
+	git checkout --detach B2~ &&
 	git log -1 --pretty=format:%b >expected-message &&
 	FAKE_LINES="1 fixup 2 fixup_-C 3 fixup_-C 4" git rebase -i A &&
 	test_cmp_rev HEAD^ A &&
@@ -190,13 +197,16 @@ test_expect_success 'first fixup -C commented out in sequence fixup fixup -C fix
 test_expect_success 'multiple fixup -c opens editor once' '
 	test_when_finished "test_might_fail git rebase --abort" &&
 	git checkout --detach A3 &&
-	base=$(git rev-parse HEAD~4) &&
-	FAKE_COMMIT_MESSAGE="Modified-A3" \
+	git log -1 --pretty=format:%B >expected-message &&
+	test_write_lines "" "Modified-A3" >>expected-message &&
+	FAKE_COMMIT_AMEND="Modified-A3" \
 		FAKE_LINES="1 fixup_-C 2 fixup_-c 3 fixup_-c 4" \
 		EXPECT_HEADER_COUNT=4 \
-		git rebase -i $base &&
-	test_cmp_rev $base HEAD^ &&
-	test 1 = $(git show | grep Modified-A3 | wc -l)
+		git rebase -i A &&
+	test_cmp_rev HEAD^ A &&
+	get_author HEAD >actual-author &&
+	test_cmp expected-author actual-author &&
+	test_commit_message HEAD expected-message
 '
 
 test_expect_success 'sequence squash, fixup & fixup -c gives combined message' '
@@ -211,12 +221,12 @@ test_expect_success 'sequence squash, fixup & fixup -c gives combined message' '
 '
 
 test_expect_success 'fixup -C works upon --autosquash with amend!' '
-	git checkout --detach branch &&
+	git checkout --detach B3 &&
 	FAKE_COMMIT_AMEND=squashed \
 		FAKE_MESSAGE_COPY=actual-squash-message \
 		git -c commit.status=false rebase -ik --autosquash \
 						--signoff A &&
-	git diff-tree --exit-code --patch HEAD branch -- &&
+	git diff-tree --exit-code --patch HEAD B3 -- &&
 	test_cmp_rev HEAD^ A &&
 	test_i18ncmp "$TEST_DIRECTORY/t3437/expected-squash-message" \
 		actual-squash-message