diff --git a/Documentation/git-branch.txt b/Documentation/git-branch.txt
index 092f1bcf9f..e465298571 100644
--- a/Documentation/git-branch.txt
+++ b/Documentation/git-branch.txt
@@ -215,11 +215,13 @@ start-point is either a local or remote-tracking branch.
 
 --merged [<commit>]::
 	Only list branches whose tips are reachable from the
-	specified commit (HEAD if not specified). Implies `--list`.
+	specified commit (HEAD if not specified). Implies `--list`,
+	incompatible with `--no-merged`.
 
 --no-merged [<commit>]::
 	Only list branches whose tips are not reachable from the
-	specified commit (HEAD if not specified). Implies `--list`.
+	specified commit (HEAD if not specified). Implies `--list`,
+	incompatible with `--merged`.
 
 <branchname>::
 	The name of the branch to create or delete.
diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index 111e1be6f5..4d55893712 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/Documentation/git-for-each-ref.txt
@@ -69,11 +69,13 @@ OPTIONS
 
 --merged [<object>]::
 	Only list refs whose tips are reachable from the
-	specified commit (HEAD if not specified).
+	specified commit (HEAD if not specified),
+	incompatible with `--no-merged`.
 
 --no-merged [<object>]::
 	Only list refs whose tips are not reachable from the
-	specified commit (HEAD if not specified).
+	specified commit (HEAD if not specified),
+	incompatible with `--merged`.
 
 --contains [<object>]::
 	Only list refs which contain the specified commit (HEAD if not
diff --git a/Documentation/git-tag.txt b/Documentation/git-tag.txt
index 3abf912782..448fdf3743 100644
--- a/Documentation/git-tag.txt
+++ b/Documentation/git-tag.txt
@@ -126,11 +126,11 @@ This option is only applicable when listing tags without annotation lines.
 
 --merged [<commit>]::
 	Only list tags whose commits are reachable from the specified
-	commit (`HEAD` if not specified).
+	commit (`HEAD` if not specified), incompatible with `--no-merged`.
 
 --no-merged [<commit>]::
 	Only list tags whose commits are not reachable from the specified
-	commit (`HEAD` if not specified).
+	commit (`HEAD` if not specified), incompatible with `--merged`.
 
 --points-at <object>::
 	Only list tags of the given object.
diff --git a/ref-filter.c b/ref-filter.c
index 7eeecc608f..81da37b5b9 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -2084,8 +2084,17 @@ int parse_opt_merge_filter(const struct option *opt, const char *arg, int unset)
 {
 	struct ref_filter *rf = opt->value;
 	unsigned char sha1[20];
+	int no_merged = starts_with(opt->long_name, "no");
 
-	rf->merge = starts_with(opt->long_name, "no")
+	if (rf->merge) {
+		if (no_merged) {
+			return opterror(opt, "is incompatible with --merged", 0);
+		} else {
+			return opterror(opt, "is incompatible with --no-merged", 0);
+		}
+	}
+
+	rf->merge = no_merged
 		? REF_FILTER_MERGED_OMIT
 		: REF_FILTER_MERGED_INCLUDE;
 
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index e36ed3b4e1..f286f39b45 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -953,6 +953,10 @@ test_expect_success '--merged catches invalid object names' '
 	test_must_fail git branch --merged 0000000000000000000000000000000000000000
 '
 
+test_expect_success '--merged is incompatible with --no-merged' '
+	test_must_fail git branch --merged HEAD --no-merged HEAD
+'
+
 test_expect_success 'tracking with unexpected .fetch refspec' '
 	rm -rf a b c d &&
 	git init a &&
diff --git a/t/t6302-for-each-ref-filter.sh b/t/t6302-for-each-ref-filter.sh
index a09a1a46ef..d36d5dc124 100755
--- a/t/t6302-for-each-ref-filter.sh
+++ b/t/t6302-for-each-ref-filter.sh
@@ -421,4 +421,8 @@ test_expect_success 'check %(if:notequals=<string>)' '
 	test_cmp expect actual
 '
 
+test_expect_success '--merged is incompatible with --no-merged' '
+	test_must_fail git for-each-ref --merged HEAD --no-merged HEAD
+'
+
 test_done
diff --git a/t/t7004-tag.sh b/t/t7004-tag.sh
index b4698ab5f5..45790664c1 100755
--- a/t/t7004-tag.sh
+++ b/t/t7004-tag.sh
@@ -1748,6 +1748,10 @@ test_expect_success '--merged cannot be used in non-list mode' '
 	test_must_fail git tag --merged=mergetest-2 foo
 '
 
+test_expect_success '--merged is incompatible with --no-merged' '
+	test_must_fail git tag --merged HEAD --no-merged HEAD
+'
+
 test_expect_success '--merged shows merged tags' '
 	cat >expect <<-\EOF &&
 	mergetest-1