diff --git a/src/check_expr.cpp b/src/check_expr.cpp
index a30f83e7e..fcd7818bc 100644
--- a/src/check_expr.cpp
+++ b/src/check_expr.cpp
@@ -1328,6 +1328,19 @@ bool is_polymorphic_type_assignable(CheckerContext *c, Type *poly, Type *source,
 			}
 		} 
 		return false;
+
+	case Type_SimdVector:
+		if (source->kind == Type_SimdVector) {
+			if (poly->SimdVector.generic_count != nullptr) {
+				if (!polymorphic_assign_index(&poly->SimdVector.generic_count, &poly->SimdVector.count, source->SimdVector.count)) {
+					return false;
+				}
+			}
+			if (poly->SimdVector.count == source->SimdVector.count) {
+				return is_polymorphic_type_assignable(c, poly->SimdVector.elem, source->SimdVector.elem, true, modify_type);
+			}
+		}
+		return false;
 	}
 	return false;
 }
diff --git a/src/check_type.cpp b/src/check_type.cpp
index 088853810..354ab6e94 100644
--- a/src/check_type.cpp
+++ b/src/check_type.cpp
@@ -2803,14 +2803,14 @@ bool check_type_internal(CheckerContext *ctx, Ast *e, Type **type, Type *named_t
 						goto array_end;
 					}
 					if (is_type_polymorphic(elem)) {
-						count = 1;
+						// Ignore
 					} else if (count < 1 || !is_power_of_two(count)) {
 						error(at->count, "Invalid length for 'intrinsics.simd_vector', expected a power of two length, got '%lld'", cast(long long)count);
 						*type = alloc_type_array(elem, count, generic_type);
 						goto array_end;
 					}
 
-					*type = alloc_type_simd_vector(count, elem);
+					*type = alloc_type_simd_vector(count, elem, generic_type);
 				} else {
 					error(at->tag, "Invalid tag applied to array, got #%.*s", LIT(name));
 					*type = alloc_type_array(elem, count, generic_type);
diff --git a/src/types.cpp b/src/types.cpp
index 755f78f1c..2d5709b19 100644
--- a/src/types.cpp
+++ b/src/types.cpp
@@ -261,6 +261,7 @@ struct TypeProc {
 	TYPE_KIND(SimdVector, struct {                            \
 		i64   count;                                      \
 		Type *elem;                                       \
+		Type *generic_count;                              \
 	})                                                        \
 	TYPE_KIND(RelativePointer, struct {                       \
 		Type *pointer_type;                               \
@@ -1085,10 +1086,11 @@ Type *alloc_type_bit_set() {
 
 
 
-Type *alloc_type_simd_vector(i64 count, Type *elem) {
+Type *alloc_type_simd_vector(i64 count, Type *elem, Type *generic_count=nullptr) {
 	Type *t = alloc_type(Type_SimdVector);
 	t->SimdVector.count = count;
 	t->SimdVector.elem = elem;
+	t->SimdVector.generic_count = generic_count;
 	return t;
 }
 
@@ -2078,6 +2080,11 @@ bool is_type_polymorphic(Type *t, bool or_specialized=false) {
 			return true;
 		}
 		return is_type_polymorphic(t->Array.elem, or_specialized);
+	case Type_SimdVector:
+		if (t->SimdVector.generic_count != nullptr) {
+			return true;
+		}
+		return is_type_polymorphic(t->SimdVector.elem, or_specialized);
 	case Type_DynamicArray:
 		return is_type_polymorphic(t->DynamicArray.elem, or_specialized);
 	case Type_Slice: