diff --git a/libasn1compiler/asn1c_C.c b/libasn1compiler/asn1c_C.c
index c51f9982..e3669fd2 100644
--- a/libasn1compiler/asn1c_C.c
+++ b/libasn1compiler/asn1c_C.c
@@ -410,6 +410,20 @@ asn1c_lang_C_type_SEQUENCE(arg_t *arg) {
 	return asn1c_lang_C_type_SEQUENCE_def(arg, ioc_tao.ioct ? &ioc_tao : 0);
 }
 
+static void
+emit_tag2member_reference(arg_t *arg, asn1p_expr_t *expr,
+                          unsigned tag2el_count) {
+    if(tag2el_count) {
+        if(C99_MODE) OUT(".tag2el = ");
+        OUT("asn_MAP_%s_tag2el_%d,\n", MKID(expr), expr->_type_unique_index);
+        if(C99_MODE) OUT(".tag2el_count = ");
+        OUT("%d,\t/* Count of tags in the map */\n", tag2el_count);
+    } else {
+        OUT("0,\t/* No top level tags */\n");
+        OUT("0,\t/* No tags in the map */\n");
+    }
+}
+
 static int
 asn1c_lang_C_type_SEQUENCE_def(arg_t *arg, asn1c_ioc_table_and_objset_t *opt_ioc) {
 	asn1p_expr_t *expr = arg->expr;
@@ -540,16 +554,7 @@ asn1c_lang_C_type_SEQUENCE_def(arg_t *arg, asn1c_ioc_table_and_objset_t *opt_ioc
 		out_name_chain(arg, ONC_avoid_keywords); OUT("),\n");
 	OUT("offsetof(struct ");
 		out_name_chain(arg, ONC_avoid_keywords); OUT(", _asn_ctx),\n");
-
-	if(tag2el_count) {
-		OUT("asn_MAP_%s_tag2el_%d,\n",
-			MKID(expr),
-			expr->_type_unique_index);
-		OUT("%d,\t/* Count of tags in the map */\n", tag2el_count);
-	} else {
-		OUT("0,\t/* No top level tags */\n");
-		OUT("0,\t/* No tags in the map */\n");
-	}
+    emit_tag2member_reference(arg, expr, tag2el_count);
 	if(roms_count + aoms_count) {
 		OUT("asn_MAP_%s_oms_%d,\t/* Optional members */\n",
 			MKID(expr), expr->_type_unique_index);
@@ -784,9 +789,8 @@ asn1c_lang_C_type_SET_def(arg_t *arg) {
 		OUT("offsetof(struct ");
 			out_name_chain(arg, ONC_avoid_keywords);
 		OUT(", _presence_map),\n");
+		emit_tag2member_reference(arg, expr, tag2el_count);
 		p = MKID(expr);
-		OUT("asn_MAP_%s_tag2el_%d,\n", p, expr->_type_unique_index);
-		OUT("%d,\t/* Count of tags in the map */\n", tag2el_count);
 		if(tag2el_cxer)
 			OUT("asn_MAP_%s_tag2el_cxer_%d,\n",
 				p, expr->_type_unique_index);
@@ -1227,9 +1231,7 @@ asn1c_lang_C_type_CHOICE_def(arg_t *arg) {
 		OUT("sizeof(((struct ");
 			out_name_chain(arg, ONC_avoid_keywords);
 		OUT(" *)0)->present),\n");
-		OUT("asn_MAP_%s_tag2el_%d,\n",
-			MKID(expr), expr->_type_unique_index);
-		OUT("%d,\t/* Count of tags in the map */\n", tag2el_count);
+		emit_tag2member_reference(arg, expr, tag2el_count);
 		if(C99_MODE) OUT(".canonical_order = ");
 		if(cmap) OUT("asn_MAP_%s_cmap_%d,\t/* Canonically sorted */\n",
 			MKID(expr), expr->_type_unique_index);
@@ -2715,13 +2717,35 @@ emit_member_type_selector(arg_t *arg, asn1p_expr_t *expr, asn1c_ioc_table_and_ob
     const asn1p_ref_t *objset_ref =
         asn1c_get_information_object_set_reference_from_constraint(arg, crc);
 
-    if(!objset_ref || objset_ref->comp_count != 1) {
-        FATAL("Reference %s does not look like an object set type %s",
-              asn1p_constraint_string(crc), asn1p_ref_string(objset_ref));
+    if(!objset_ref) {
+        FATAL("Constraint %s does not look like it referst to a set type %s",
+              asn1p_constraint_string(crc),
+              opt_ioc->objset->Identifier);
         return -1;
     }
 
-    const char *objset_name = objset_ref->components[0].name;
+    const char *objset_name;
+    if(objset_ref->comp_count == 1) {
+        objset_name = objset_ref->components[0].name;
+    } else if(objset_ref->comp_count == 2) {
+        if(strcmp(objset_ref->components[0].name,
+                  opt_ioc->objset->module->ModuleName)
+           != 0) {
+            FATAL(
+                "Composite reference %s (from %s) does not look like it refers "
+                "to the same module as %s from an object set type %s",
+                asn1p_ref_string(objset_ref), asn1p_constraint_string(crc),
+                opt_ioc->objset->module->ModuleName,
+                opt_ioc->objset->Identifier);
+            return -1;
+        }
+        objset_name = objset_ref->components[1].name;
+    } else {
+        FATAL("Reference %s (from %s) does not look like an object set type %s",
+              asn1p_ref_string(objset_ref), asn1p_constraint_string(crc),
+              opt_ioc->objset->Identifier);
+        return -1;
+    }
     if(strcmp(objset_name, opt_ioc->objset->Identifier) != 0) {
         FATAL("Object Set references do not match: %s != %s", objset_name,
               opt_ioc->objset->Identifier);
diff --git a/libasn1fix/asn1fix_cws.c b/libasn1fix/asn1fix_cws.c
index 8965b962..1106e555 100644
--- a/libasn1fix/asn1fix_cws.c
+++ b/libasn1fix/asn1fix_cws.c
@@ -1,8 +1,6 @@
 #include "asn1fix_internal.h"
 #include "asn1fix_cws.h"
 
-const char *asn1p_constraint_string(const asn1p_constraint_t *);
-
 static int _asn1f_parse_class_object_data(arg_t *, asn1p_expr_t *eclass,
 		struct asn1p_ioc_row_s *row, asn1p_wsyntx_t *syntax,
 		const uint8_t *buf, const uint8_t *bend,
@@ -181,25 +179,28 @@ static int
 _asn1f_foreach_unparsed(arg_t *arg, const asn1p_constraint_t *ct,
                         int (*process)(const uint8_t *buf, size_t size,
                                        void *key),
-                        void *key) {
+                        void *keyp) {
+    struct parse_object_key *key = keyp;
     if(!ct) return -1;
 
     switch(ct->type) {
     default:
-        DEBUG("Constraint %s is of unknown type for CWS",
-              asn1p_constraint_string(ct));
+        DEBUG("Constraint is of unknown type %d for CWS", ct->type);
         return -1;
     case ACT_EL_EXT:    /* ... */
+        if(key) {
+            key->expr->ioc_table->extensible = 1;
+        }
         return 0;
     case ACT_CA_UNI:    /* | */
-        return _asn1f_foreach_unparsed_union(ct, process, key);
+        return _asn1f_foreach_unparsed_union(ct, process, keyp);
     case ACT_CA_CSV:    /* , */
         break;
     }
 
     for(size_t i = 0; i < ct->el_count; i++) {
         const asn1p_constraint_t *ct1 = ct->elements[i];
-        if(_asn1f_foreach_unparsed(arg, ct1, process, key) != 0) {
+        if(_asn1f_foreach_unparsed(arg, ct1, process, keyp) != 0) {
             return -1;
         }
     }