diff --git a/libasn1fix/asn1fix_param.c b/libasn1fix/asn1fix_param.c
index 1419c053..77daba13 100644
--- a/libasn1fix/asn1fix_param.c
+++ b/libasn1fix/asn1fix_param.c
@@ -112,7 +112,7 @@ resolve_expr(asn1p_expr_t *expr_to_resolve, void *resolver_arg) {
 				expr_to_resolve->reference);
 		if(!expr) return NULL;
 	} else if(expr_to_resolve->meta_type == AMT_VALUE) {
-		assert(expr_to_resolve->value);
+		if(!expr_to_resolve->value) return NULL;
 		expr = find_target_specialization_bystr(rarg,
 				expr_to_resolve->Identifier);
 		if(!expr) return NULL;
@@ -155,7 +155,7 @@ static asn1p_expr_t *
 find_target_specialization_byvalueset(resolver_arg_t *rarg, asn1p_constraint_t *ct) {
 	asn1p_ref_t *ref;
 
-	assert(ct->type == ACT_EL_TYPE);
+	if (ct->type != ACT_EL_TYPE) return NULL;
 
 	ref = ct->containedSubtype->value.v_type->reference;
 
diff --git a/tests/tests-asn1c-compiler/139-component-relation-OK.asn1.-P b/tests/tests-asn1c-compiler/139-component-relation-OK.asn1.-P
index e9af4b3b..89468a49 100644
--- a/tests/tests-asn1c-compiler/139-component-relation-OK.asn1.-P
+++ b/tests/tests-asn1c-compiler/139-component-relation-OK.asn1.-P
@@ -24,7 +24,7 @@ typedef struct Frame {
 	long	 ident;
 	struct value {
 		value_PR present;
-		union value_u {
+		union Frame__value_u {
 			PrimitiveMessage_t	 PrimitiveMessage;
 			ComplexMessage_t	 ComplexMessage;
 		} choice;
@@ -81,7 +81,7 @@ memb_ident_constraint_1(const asn_TYPE_descriptor_t *td, const void *sptr,
 }
 
 static asn_type_selector_result_t
-select_value_type(const asn_TYPE_descriptor_t *parent_type, const void *parent_sptr) {
+select_Frame_value_type(const asn_TYPE_descriptor_t *parent_type, const void *parent_sptr) {
 	asn_type_selector_result_t result = {0, 0};
 	const asn_ioc_set_t *itable = asn_IOS_FrameTypes_1;
 	size_t constraining_column = 0; /* &id */
@@ -188,7 +188,7 @@ static asn_TYPE_member_t asn_MBR_Frame_1[] = {
 		.tag = -1 /* Ambiguous tag (ANY?) */,
 		.tag_mode = 0,
 		.type = &asn_DEF_value_3,
-		.type_selector = select_value_type,
+		.type_selector = select_Frame_value_type,
 		{ .oer_constraints = 0, .per_constraints = 0, .general_constraints =  memb_value_constraint_1 },
 		0, 0, /* No default value */
 		.name = "value"
diff --git a/tests/tests-asn1c-compiler/140-component-relation-OK.asn1.-P b/tests/tests-asn1c-compiler/140-component-relation-OK.asn1.-P
index e9af4b3b..89468a49 100644
--- a/tests/tests-asn1c-compiler/140-component-relation-OK.asn1.-P
+++ b/tests/tests-asn1c-compiler/140-component-relation-OK.asn1.-P
@@ -24,7 +24,7 @@ typedef struct Frame {
 	long	 ident;
 	struct value {
 		value_PR present;
-		union value_u {
+		union Frame__value_u {
 			PrimitiveMessage_t	 PrimitiveMessage;
 			ComplexMessage_t	 ComplexMessage;
 		} choice;
@@ -81,7 +81,7 @@ memb_ident_constraint_1(const asn_TYPE_descriptor_t *td, const void *sptr,
 }
 
 static asn_type_selector_result_t
-select_value_type(const asn_TYPE_descriptor_t *parent_type, const void *parent_sptr) {
+select_Frame_value_type(const asn_TYPE_descriptor_t *parent_type, const void *parent_sptr) {
 	asn_type_selector_result_t result = {0, 0};
 	const asn_ioc_set_t *itable = asn_IOS_FrameTypes_1;
 	size_t constraining_column = 0; /* &id */
@@ -188,7 +188,7 @@ static asn_TYPE_member_t asn_MBR_Frame_1[] = {
 		.tag = -1 /* Ambiguous tag (ANY?) */,
 		.tag_mode = 0,
 		.type = &asn_DEF_value_3,
-		.type_selector = select_value_type,
+		.type_selector = select_Frame_value_type,
 		{ .oer_constraints = 0, .per_constraints = 0, .general_constraints =  memb_value_constraint_1 },
 		0, 0, /* No default value */
 		.name = "value"
diff --git a/tests/tests-asn1c-compiler/141-component-relation-OK.asn1.-P b/tests/tests-asn1c-compiler/141-component-relation-OK.asn1.-P
index 80abe317..9befb070 100644
--- a/tests/tests-asn1c-compiler/141-component-relation-OK.asn1.-P
+++ b/tests/tests-asn1c-compiler/141-component-relation-OK.asn1.-P
@@ -24,7 +24,7 @@ typedef struct Frame {
 	ConstrainedInteger_t	 ident;
 	struct value {
 		value_PR present;
-		union value_u {
+		union Frame__value_u {
 			PrimitiveMessage_t	 PrimitiveMessage;
 			ComplexMessage_t	 ComplexMessage;
 		} choice;
@@ -87,7 +87,7 @@ memb_ident_constraint_1(const asn_TYPE_descriptor_t *td, const void *sptr,
 }
 
 static asn_type_selector_result_t
-select_value_type(const asn_TYPE_descriptor_t *parent_type, const void *parent_sptr) {
+select_Frame_value_type(const asn_TYPE_descriptor_t *parent_type, const void *parent_sptr) {
 	asn_type_selector_result_t result = {0, 0};
 	const asn_ioc_set_t *itable = asn_IOS_FrameTypes_1;
 	size_t constraining_column = 0; /* &id */
@@ -194,7 +194,7 @@ static asn_TYPE_member_t asn_MBR_Frame_1[] = {
 		.tag = (ASN_TAG_CLASS_CONTEXT | (1 << 2)),
 		.tag_mode = +1,	/* EXPLICIT tag at current level */
 		.type = &asn_DEF_value_3,
-		.type_selector = select_value_type,
+		.type_selector = select_Frame_value_type,
 		{ .oer_constraints = 0, .per_constraints = 0, .general_constraints =  memb_value_constraint_1 },
 		0, 0, /* No default value */
 		.name = "value"
diff --git a/tests/tests-asn1c-compiler/144-ios-parameterization-OK.asn1.-P b/tests/tests-asn1c-compiler/144-ios-parameterization-OK.asn1.-P
index 2f0a421a..9020ba7f 100644
--- a/tests/tests-asn1c-compiler/144-ios-parameterization-OK.asn1.-P
+++ b/tests/tests-asn1c-compiler/144-ios-parameterization-OK.asn1.-P
@@ -86,7 +86,7 @@ typedef struct SpecializedContent_30P0 {
 	long	 id;
 	struct value {
 		value_PR present;
-		union value_u {
+		union SpecializedContent_30P0__value_u {
 			long	 INTEGER;
 			BOOLEAN_t	 BOOLEAN;
 		} choice;
@@ -141,7 +141,7 @@ memb_id_constraint_1(const asn_TYPE_descriptor_t *td, const void *sptr,
 }
 
 static asn_type_selector_result_t
-select_value_type(const asn_TYPE_descriptor_t *parent_type, const void *parent_sptr) {
+select_SpecializedContent_30P0_value_type(const asn_TYPE_descriptor_t *parent_type, const void *parent_sptr) {
 	asn_type_selector_result_t result = {0, 0};
 	const asn_ioc_set_t *itable = asn_IOS_RegionalExtension_1;
 	size_t constraining_column = 0; /* &id */
@@ -248,7 +248,7 @@ asn_TYPE_member_t asn_MBR_SpecializedContent_30P0_1[] = {
 		.tag = -1 /* Ambiguous tag (ANY?) */,
 		.tag_mode = 0,
 		.type = &asn_DEF_value_3,
-		.type_selector = select_value_type,
+		.type_selector = select_SpecializedContent_30P0_value_type,
 		{ .oer_constraints = 0, .per_constraints = 0, .general_constraints =  memb_value_constraint_1 },
 		0, 0, /* No default value */
 		.name = "value"
diff --git a/tests/tests-asn1c-compiler/146-ios-parameterization-per-OK.asn1.-Pgen-PER b/tests/tests-asn1c-compiler/146-ios-parameterization-per-OK.asn1.-Pgen-PER
index e17e676e..b232b5b3 100644
--- a/tests/tests-asn1c-compiler/146-ios-parameterization-per-OK.asn1.-Pgen-PER
+++ b/tests/tests-asn1c-compiler/146-ios-parameterization-per-OK.asn1.-Pgen-PER
@@ -86,7 +86,7 @@ typedef struct SpecializedContent_30P0 {
 	long	 id;
 	struct value {
 		value_PR present;
-		union value_u {
+		union SpecializedContent_30P0__value_u {
 			long	 INTEGER;
 			BOOLEAN_t	 BOOLEAN;
 		} choice;
@@ -141,7 +141,7 @@ memb_id_constraint_1(const asn_TYPE_descriptor_t *td, const void *sptr,
 }
 
 static asn_type_selector_result_t
-select_value_type(const asn_TYPE_descriptor_t *parent_type, const void *parent_sptr) {
+select_SpecializedContent_30P0_value_type(const asn_TYPE_descriptor_t *parent_type, const void *parent_sptr) {
 	asn_type_selector_result_t result = {0, 0};
 	const asn_ioc_set_t *itable = asn_IOS_RegionalExtension_1;
 	size_t constraining_column = 0; /* &id */
@@ -264,7 +264,7 @@ asn_TYPE_member_t asn_MBR_SpecializedContent_30P0_1[] = {
 		.tag = -1 /* Ambiguous tag (ANY?) */,
 		.tag_mode = 0,
 		.type = &asn_DEF_value_3,
-		.type_selector = select_value_type,
+		.type_selector = select_SpecializedContent_30P0_value_type,
 		{ .oer_constraints = 0, .per_constraints = &asn_PER_memb_value_constr_3, .general_constraints =  memb_value_constraint_1 },
 		0, 0, /* No default value */
 		.name = "value"