diff --git a/js/src/ctypes/CTypes.cpp b/js/src/ctypes/CTypes.cpp
index 2fe4187fbfb..640434db8d6 100644
--- a/js/src/ctypes/CTypes.cpp
+++ b/js/src/ctypes/CTypes.cpp
@@ -4963,7 +4963,7 @@ StructType::DefineInternal(JSContext* cx, JSObject* typeObj_, JSObject* fieldsOb
 
       // Add field name to the hash
       FieldInfo info;
-      info.mType = nullptr; // Value of fields are not yet traceable here.
+      info.mType = fieldType;
       info.mIndex = i;
       info.mOffset = fieldOffset;
       ASSERT_OK(fields->add(entryPtr, name, info));
@@ -4996,12 +4996,6 @@ StructType::DefineInternal(JSContext* cx, JSObject* typeObj_, JSObject* fieldsOb
   if (!SizeTojsval(cx, structSize, &sizeVal))
     return false;
 
-  for (FieldInfoHash::Range r = fields->all(); !r.empty(); r.popFront()) {
-    FieldInfo& field = r.front().value();
-    MOZ_ASSERT(field.mIndex < fieldRoots.length());
-    field.mType = &fieldRoots[field.mIndex].toObject();
-  }
-
   JS_SetReservedSlot(typeObj, SLOT_FIELDINFO, PRIVATE_TO_JSVAL(fields.release()));
 
   JS_SetReservedSlot(typeObj, SLOT_SIZE, sizeVal);
diff --git a/js/src/jit-test/tests/ctypes/bug1155985.js b/js/src/jit-test/tests/ctypes/bug1155985.js
deleted file mode 100644
index 54c24d4badf..00000000000
--- a/js/src/jit-test/tests/ctypes/bug1155985.js
+++ /dev/null
@@ -1,14 +0,0 @@
-function test() {
-  for (let i = 0; i < 100; i++) {
-    let test_struct = ctypes.StructType("test_struct", [{ "x": ctypes.int32_t },
-                                                        { "bar": ctypes.uint32_t }]);
-
-    try {
-      new test_struct("foo", "x");
-    } catch (e) {
-    }
-  }
-}
-
-if (typeof ctypes === "object")
-  test();