diff --git a/libasn1fix/asn1fix_bitstring.c b/libasn1fix/asn1fix_bitstring.c
index f8adc753f25a16b197f0dc1ec0c1958bdef12950..e2f2434a8a995b1bb85df2b7188da9530d61df48 100644
--- a/libasn1fix/asn1fix_bitstring.c
+++ b/libasn1fix/asn1fix_bitstring.c
@@ -36,17 +36,28 @@ static int
 asn1f_fix_bit_string_type(arg_t *arg) {
 	asn1p_expr_t *expr = arg->expr;
 	asn1p_expr_t *v;
+	int r_value = 0;
+	int ret;
 
 	TQ_FOR(v, &(expr->members), next) {
+		/* Check identifier uniqueness as per 21.4 */
+		ret = asn1f_check_unique_expr_child(arg, v, 0);
+		RET2RVAL(ret, r_value);
+
+		if(v->expr_type == A1TC_EXTENSIBLE) {
+			FATAL("Extension marker (...) is not allowed "
+				"as a BIT STRING NamedBit at line %d ",
+				v->_lineno);
+			return -1;
+		}
 		if(v->expr_type != A1TC_UNIVERVAL) {
 			FATAL("BIT STRING value at line %d "
-				"is not an identifier",
-				v->_lineno);
+				"is not an identifier", v->_lineno);
 			return -1;
 		}
 	}
 
-	return 0;
+	return r_value;
 }
 
 static int
diff --git a/libasn1fix/asn1fix_enum.c b/libasn1fix/asn1fix_enum.c
index ce2fc2fc646a4cb347392dc94bed7dac915f07f5..cf03914f5c53081cb9749fbd28f6b0521ea70e36 100644
--- a/libasn1fix/asn1fix_enum.c
+++ b/libasn1fix/asn1fix_enum.c
@@ -34,8 +34,7 @@ asn1f_fix_enum(arg_t *arg) {
 		 */
 		if(ev->expr_type == A1TC_EXTENSIBLE) {
 			if(ext_marker) {
-				arg->eh(1,
-				"Enumeration %s at line %d: "
+				FATAL("Enumeration %s at line %d: "
 				"Second extension marker is not allowed",
 				expr->Identifier,
 				ev->_lineno);
diff --git a/libasn1fix/asn1fix_integer.c b/libasn1fix/asn1fix_integer.c
index 8a144911803f189c5e2eb68e48b821d83e0d80f6..0302acd25d80f8199e78ae1554166059180f2e6d 100644
--- a/libasn1fix/asn1fix_integer.c
+++ b/libasn1fix/asn1fix_integer.c
@@ -38,20 +38,17 @@ asn1f_fix_integer(arg_t *arg) {
 		 * Found "...", check correctness.
 		 */
 		if(iv->expr_type == A1TC_EXTENSIBLE) {
-			arg->eh(1,
-				"INTEGER %s at line %d: "
+			FATAL("INTEGER %s at line %d: "
 				"Extension marker is not allowed",
 				expr->Identifier,
-				iv->_lineno
-			);
+				iv->_lineno);
 			rvalue = -1;
 			continue;
 		}
 
 		if(iv->Identifier == NULL
 		|| iv->expr_type != A1TC_UNIVERVAL) {
-			arg->eh(1,
-				"INTEGER %s at line %d: "
+			FATAL("INTEGER %s at line %d: "
 				"Unsupported enumeration element %s",
 				expr->Identifier,
 				iv->_lineno,
@@ -62,8 +59,7 @@ asn1f_fix_integer(arg_t *arg) {
 		}
 
 		if(iv->value == NULL) {
-			arg->eh(1,
-				"INTEGER %s at line %d: "
+			FATAL("INTEGER %s at line %d: "
 				"Value for the identifier %s "
 				"must be set explicitly",
 				expr->Identifier,
@@ -84,8 +80,7 @@ asn1f_fix_integer(arg_t *arg) {
 		}
 
 		if(iv->value->type != ATV_INTEGER) {
-			arg->eh(1,
-				"INTEGER %s at line %d: "
+			FATAL("INTEGER %s at line %d: "
 				"Value for the identifier %s "
 				"is not compatible with INTEGER type",
 				expr->Identifier,
diff --git a/libasn1fix/asn1fix_misc.c b/libasn1fix/asn1fix_misc.c
index 72317aa24edb293a92b91fd65e9d8fcb728cbece..9e8cc07fbec78217a13d9215c508bf985a8d49c9 100644
--- a/libasn1fix/asn1fix_misc.c
+++ b/libasn1fix/asn1fix_misc.c
@@ -294,8 +294,7 @@ asn1f_check_unique_expr_child(arg_t *arg, asn1p_expr_t *child,
 			msg = opt_compare
 				?"Expressions clash"
 				:"Identifiers name clash";
-			arg->eh(1,
-				"%s: "
+			FATAL("%s: "
 				"\"%s\" at line %d has similar %s with "
 				"\"%s\" at line %d",
 				msg,
diff --git a/tests/113-bit-string-SE.asn1 b/tests/113-bit-string-SE.asn1
new file mode 100644
index 0000000000000000000000000000000000000000..110e7644d623023b84201016839b78eae474235e
--- /dev/null
+++ b/tests/113-bit-string-SE.asn1
@@ -0,0 +1,16 @@
+
+-- SE: Semantic error
+
+-- iso.org.dod.internet.private.enterprise (1.3.6.1.4.1)
+-- .spelio.software.asn1c.test (9363.1.5.1)
+-- .113
+
+ModuleBitStringExtensibility
+	{ iso org(3) dod(6) internet (1) private(4) enterprise(1)
+		spelio(9363) software(1) asn1c(5) test(1) 113 }
+	DEFINITIONS ::=
+BEGIN
+
+	T ::= BIT STRING { one(1), one(2) }
+
+END