--- a/dom/bindings/Codegen.py
+++ b/dom/bindings/Codegen.py
@@ -3537,27 +3537,30 @@ def typeNeedsCx(type, descriptorProvider
 
 # Returns a tuple consisting of a CGThing containing the type of the return
 # value, or None if there is no need for a return value, and a boolean signaling
 # whether the return value is passed in an out parameter.
 #
 # Whenever this is modified, please update CGNativeMember.getRetvalInfo as
 # needed
 def getRetvalDeclarationForType(returnType, descriptorProvider,
-                                resultAlreadyAddRefed):
+                                resultAlreadyAddRefed,
+                                isMember=False):
     if returnType is None or returnType.isVoid():
         # Nothing to declare
         return None, False
     if returnType.isPrimitive() and returnType.tag() in builtinNames:
         result = CGGeneric(builtinNames[returnType.tag()])
         if returnType.nullable():
             result = CGWrapper(result, pre="Nullable<", post=">")
         return result, False
     if returnType.isString():
-        return CGGeneric("nsString"), True
+        if isMember:
+            return CGGeneric("nsString"), True
+        return CGGeneric("DOMString"), True
     if returnType.isEnum():
         if returnType.nullable():
             raise TypeError("We don't support nullable enum return values")
         return CGGeneric(returnType.inner.identifier.name), False
     if returnType.isGeckoInterface():
         result = CGGeneric(descriptorProvider.getDescriptor(
             returnType.unroll().inner.identifier.name).nativeType)
         if resultAlreadyAddRefed:
@@ -3577,17 +3580,18 @@ def getRetvalDeclarationForType(returnTy
     if returnType.isSequence():
         nullable = returnType.nullable()
         if nullable:
             returnType = returnType.inner
         # If our result is already addrefed, use the right type in the
         # sequence argument here.
         (result, _) = getRetvalDeclarationForType(returnType.inner,
                                                   descriptorProvider,
-                                                  resultAlreadyAddRefed)
+                                                  resultAlreadyAddRefed,
+                                                  isMember=True)
         result = CGWrapper(result, pre="nsTArray< ", post=" >")
         if nullable:
             result = CGWrapper(result, pre="Nullable< ", post=" >")
         return result, True
     if returnType.isDictionary():
         nullable = returnType.nullable()
         result = CGGeneric(
             CGDictionary.makeDictionaryName(returnType.unroll().inner,