diff --git a/src/lib-sieve/sieve-comparators.c b/src/lib-sieve/sieve-comparators.c
index a66b28e2edf4611e1b0bf114113902bda0b38e25..c682031accb81ee5fa36a1dfadc5703cdf6d3523 100644
--- a/src/lib-sieve/sieve-comparators.c
+++ b/src/lib-sieve/sieve-comparators.c
@@ -140,16 +140,11 @@ static bool tag_comparator_validate
 	/* Check syntax:
 	 *   ":comparator" <comparator-name: string>
 	 */
-	if ( (*arg)->type != SAAT_STRING ) {
-		sieve_argument_validate_error(valdtr, *arg,
-			":comparator tag requires one string argument, but %s was found",
-			sieve_ast_argument_name(*arg) );
+	if ( !sieve_validate_tag_parameter
+		(valdtr, cmd, tag, *arg, NULL, 0, SAAT_STRING, FALSE) ) {
 		return FALSE;
 	}
 
-	if ( !sieve_validator_argument_activate(valdtr, cmd, *arg, FALSE) )
-		return FALSE;
-
 	/* FIXME: We can currently only handle string literal argument, so
 	 * variables are not allowed.
 	 */
diff --git a/tests/compile/errors.svtest b/tests/compile/errors.svtest
index b2c94ab95e7db0440cdb4360ec84276d24acb233..c2bc29251d745d10ab216073d2a3c1ecd06a66a8 100644
--- a/tests/compile/errors.svtest
+++ b/tests/compile/errors.svtest
@@ -242,6 +242,20 @@ test "Keep errors (FIXME: count only)" {
 	}
 }
 
+/*
+ * COMPARATOR errors
+ */
+
+test "COMPARATOR errors (FIXME: count only)" {
+	if test_script_compile "errors/comparator.sieve" {
+		test_fail "compile should have failed.";
+	}
+
+	if not test_error :count "eq" :comparator "i;ascii-numeric" "6" {
+		test_fail "wrong number of errors reported";
+	}
+}
+
 /*
  * ADDRESS-PART errors
  */
diff --git a/tests/compile/errors/comparator.sieve b/tests/compile/errors/comparator.sieve
new file mode 100644
index 0000000000000000000000000000000000000000..368b56bfcbd7e78692c741d88acce52e70aa0d55
--- /dev/null
+++ b/tests/compile/errors/comparator.sieve
@@ -0,0 +1,21 @@
+/*
+ * Address part errors
+ *
+ * Total errors: 5 (+1 = 6)
+ */
+
+# 1: No argument
+if address :comparator { }
+
+# 2: Number argument
+if address :comparator 1 "from" "frop" { }
+
+# 3: String list argument
+if address :comparator ["a", "b"] "from" "frop" { }
+
+# 4: Unknown tag
+if address :comparator :frop "from" "frop" { }
+
+# 5: Known tag
+if address :comparator :all "from" "frop" { }
+