diff --git a/src/compiler.ts b/src/compiler.ts
index 4341992c34..891a0f57e7 100644
--- a/src/compiler.ts
+++ b/src/compiler.ts
@@ -9965,8 +9965,14 @@ export class Compiler extends DiagnosticEmitter {
       case TypeKind.STRINGREF:
       case TypeKind.STRINGVIEW_WTF8:
       case TypeKind.STRINGVIEW_WTF16:
-      case TypeKind.STRINGVIEW_ITER: return module.ref_null(type.toRef());
-      case TypeKind.I31REF: return module.i31_new(module.i32(0));
+      case TypeKind.STRINGVIEW_ITER: {
+        // TODO: what if not nullable?
+        return module.ref_null(type.toRef());
+      }
+      case TypeKind.I31REF: {
+        if (type.is(TypeFlags.NULLABLE)) return module.ref_null(type.toRef());
+        return module.i31_new(module.i32(0));
+      }
     }
   }
 
diff --git a/src/types.ts b/src/types.ts
index 9a2f0361d6..65d131dcdd 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -11,9 +11,12 @@ import {
 
 import {
   TypeRef,
-  createType
+  createType,
+  HeapTypeRef
 } from "./module";
 
+import * as binaryen from "./glue/binaryen";
+
 /** Indicates the kind of a type. */
 export const enum TypeKind {
   /** A 1-bit unsigned integer. */
@@ -583,7 +586,7 @@ export class Type {
   /** Converts this type to its respective type reference. */
   toRef(): TypeRef {
     switch (this.kind) {
-      default: assert(false);
+      default: assert(false); // TODO: Concrete struct, array and signature types
       case TypeKind.BOOL:
       case TypeKind.I8:
       case TypeKind.I16:
@@ -598,17 +601,36 @@ export class Type {
       case TypeKind.F32:  return TypeRef.F32;
       case TypeKind.F64:  return TypeRef.F64;
       case TypeKind.V128: return TypeRef.V128;
-      // TODO: nullable/non-nullable refs have different type refs
-      case TypeKind.FUNCREF: return TypeRef.Funcref;
-      case TypeKind.EXTERNREF: return TypeRef.Externref;
-      case TypeKind.ANYREF: return TypeRef.Anyref;
-      case TypeKind.EQREF: return TypeRef.Eqref;
-      case TypeKind.I31REF: return TypeRef.I31ref;
-      case TypeKind.DATAREF: return TypeRef.Dataref;
-      case TypeKind.STRINGREF: return TypeRef.Stringref;
-      case TypeKind.STRINGVIEW_WTF8: return TypeRef.StringviewWTF8;
-      case TypeKind.STRINGVIEW_WTF16: return TypeRef.StringviewWTF16;
-      case TypeKind.STRINGVIEW_ITER: return TypeRef.StringviewIter;
+      case TypeKind.FUNCREF: {
+        return binaryen._BinaryenTypeFromHeapType(HeapTypeRef.Func, this.is(TypeFlags.NULLABLE));
+      }
+      case TypeKind.EXTERNREF: {
+        return binaryen._BinaryenTypeFromHeapType(HeapTypeRef.Ext, this.is(TypeFlags.NULLABLE));
+      }
+      case TypeKind.ANYREF: {
+        return binaryen._BinaryenTypeFromHeapType(HeapTypeRef.Any, this.is(TypeFlags.NULLABLE));
+      }
+      case TypeKind.EQREF: {
+        return binaryen._BinaryenTypeFromHeapType(HeapTypeRef.Eq, this.is(TypeFlags.NULLABLE));
+      }
+      case TypeKind.I31REF: {
+        return binaryen._BinaryenTypeFromHeapType(HeapTypeRef.I31, this.is(TypeFlags.NULLABLE));
+      }
+      case TypeKind.DATAREF: {
+        return binaryen._BinaryenTypeFromHeapType(HeapTypeRef.Data, this.is(TypeFlags.NULLABLE));
+      }
+      case TypeKind.STRINGREF: {
+        return binaryen._BinaryenTypeFromHeapType(HeapTypeRef.String, this.is(TypeFlags.NULLABLE));
+      }
+      case TypeKind.STRINGVIEW_WTF8: {
+        return binaryen._BinaryenTypeFromHeapType(HeapTypeRef.StringviewWTF8, this.is(TypeFlags.NULLABLE));
+      }
+      case TypeKind.STRINGVIEW_WTF16: {
+        return binaryen._BinaryenTypeFromHeapType(HeapTypeRef.StringviewWTF16, this.is(TypeFlags.NULLABLE));
+      }
+      case TypeKind.STRINGVIEW_ITER: {
+        return binaryen._BinaryenTypeFromHeapType(HeapTypeRef.StringviewIter, this.is(TypeFlags.NULLABLE));
+      }
       case TypeKind.VOID: return TypeRef.None;
     }
   }
diff --git a/tests/compiler/features/gc.debug.wat b/tests/compiler/features/gc.debug.wat
index 00ca2b1702..1cfa57402d 100644
--- a/tests/compiler/features/gc.debug.wat
+++ b/tests/compiler/features/gc.debug.wat
@@ -3,6 +3,8 @@
  (type $i32_i32_i32_i32_=>_none (func (param i32 i32 i32 i32)))
  (import "env" "abort" (func $~lib/builtins/abort (param i32 i32 i32 i32)))
  (global $features/gc/a anyref (ref.null any))
+ (global $features/gc/b i31ref (ref.null i31))
+ (global $features/gc/c dataref (ref.null data))
  (global $~lib/memory/__data_end i32 (i32.const 60))
  (global $~lib/memory/__stack_pointer (mut i32) (i32.const 16444))
  (global $~lib/memory/__heap_base i32 (i32.const 16444))
@@ -12,10 +14,12 @@
  (table $0 1 1 funcref)
  (elem $0 (i32.const 1))
  (export "a" (global $features/gc/a))
+ (export "b" (global $features/gc/b))
+ (export "c" (global $features/gc/c))
  (export "memory" (memory $0))
  (export "_start" (func $~start))
  (func $features/gc/test_i31
-  (local $ref (ref i31))
+  (local $ref i31ref)
   (local $val i32)
   (local $uval i32)
   i32.const 123
diff --git a/tests/compiler/features/gc.release.wat b/tests/compiler/features/gc.release.wat
index 1bc02d535f..3f54908d37 100644
--- a/tests/compiler/features/gc.release.wat
+++ b/tests/compiler/features/gc.release.wat
@@ -1,10 +1,14 @@
 (module
  (type $none_=>_none (func))
  (global $features/gc/a anyref (ref.null any))
+ (global $features/gc/b i31ref (ref.null i31))
+ (global $features/gc/c dataref (ref.null data))
  (memory $0 1)
  (data (i32.const 1036) ",")
  (data (i32.const 1048) "\01\00\00\00\1c\00\00\00f\00e\00a\00t\00u\00r\00e\00s\00/\00g\00c\00.\00t\00s")
  (export "a" (global $features/gc/a))
+ (export "b" (global $features/gc/b))
+ (export "c" (global $features/gc/c))
  (export "memory" (memory $0))
  (export "_start" (func $~start))
  (func $~start
diff --git a/tests/compiler/features/gc.ts b/tests/compiler/features/gc.ts
index 4346bd1ba0..838b06e051 100644
--- a/tests/compiler/features/gc.ts
+++ b/tests/compiler/features/gc.ts
@@ -10,5 +10,5 @@ test_i31();
 // constant globals
 
 export const a: anyref = null;
-// export const b: i31ref = null; // TODO: not yet nullable in Binaryen
-// export const c: dataref = null; // TODO: not yet nullable in Binaryen
+export const b: i31ref = null;
+export const c: dataref = null;