diff --git a/source/gui/scripting/JSInterface_IGUIObject.cpp b/source/gui/scripting/JSInterface_IGUIObject.cpp
index 61d5728172..64857fd2ca 100644
--- a/source/gui/scripting/JSInterface_IGUIObject.cpp
+++ b/source/gui/scripting/JSInterface_IGUIObject.cpp
@@ -433,7 +433,7 @@ JSBool JSI_IGUIObject::setProperty(JSContext* cx, JSObject* obj, jsval id, jsval
 					return JS_FALSE;
 				}
 			}
-			else if (JSVAL_IS_OBJECT(*vp) && JS_GetClass(cx, JSVAL_TO_OBJECT(*vp)) == &JSI_GUISize::JSI_class)
+			else if (JSVAL_IS_OBJECT(*vp) && JS_InstanceOf(cx, JSVAL_TO_OBJECT(*vp), &JSI_GUISize::JSI_class, NULL))
 			{
 				CClientArea area;
 				GUI<CClientArea>::GetSetting(e, propName, area);
@@ -470,7 +470,7 @@ JSBool JSI_IGUIObject::setProperty(JSContext* cx, JSObject* obj, jsval id, jsval
 					return JS_FALSE;
 				}
 			}
-			else if (JSVAL_IS_OBJECT(*vp) && JS_GetClass(cx, JSVAL_TO_OBJECT(*vp)) == &JSI_GUIColor::JSI_class)
+			else if (JSVAL_IS_OBJECT(*vp) && JS_InstanceOf(cx, JSVAL_TO_OBJECT(*vp), &JSI_GUIColor::JSI_class, NULL))
 			{
 				CColor colour;
 				JSObject* obj = JSVAL_TO_OBJECT(*vp);
diff --git a/source/scripting/ScriptGlue.cpp b/source/scripting/ScriptGlue.cpp
index 5dc3e1006c..aa0265d7c3 100644
--- a/source/scripting/ScriptGlue.cpp
+++ b/source/scripting/ScriptGlue.cpp
@@ -250,7 +250,7 @@ JSBool IssueCommand( JSContext* cx, JSObject*, uintN argc, jsval* argv, jsval* r
 	
 	CEntityList entities, msgEntities;
 
-	if (JS_GetClass(cx, JSVAL_TO_OBJECT(argv[0])) == &CEntity::JSI_class)
+	if (JS_InstanceOf(cx, JSVAL_TO_OBJECT(argv[0]), &CEntity::JSI_class, NULL))
 		entities.push_back( (ToNative<CEntity>(argv[0])) ->me);
 	else
 		entities = *EntityCollection::RetrieveSet(cx, JSVAL_TO_OBJECT(argv[0]));
@@ -340,7 +340,7 @@ JSBool RemoveFromFormation( JSContext* cx, JSObject* UNUSED(obj), uintN argc, js
 	JSU_REQUIRE_PARAMS(1);
 	
 	CEntityList entities;
-	if (JS_GetClass(cx, JSVAL_TO_OBJECT(argv[0])) == &CEntity::JSI_class)
+	if (JS_InstanceOf(cx, JSVAL_TO_OBJECT(argv[0]), &CEntity::JSI_class, NULL))
 		entities.push_back( (ToNative<CEntity>(argv[0])) ->me);
 	else
 		entities = *EntityCollection::RetrieveSet(cx, JSVAL_TO_OBJECT(argv[0]));
diff --git a/source/scriptinterface/ScriptInterface.cpp b/source/scriptinterface/ScriptInterface.cpp
index 1c6e25b16d..b8faf9f95d 100644
--- a/source/scriptinterface/ScriptInterface.cpp
+++ b/source/scriptinterface/ScriptInterface.cpp
@@ -467,7 +467,9 @@ bool ScriptInterface::IsExceptionPending(JSContext* cx)
 
 JSClass* ScriptInterface::GetClass(JSContext* cx, JSObject* obj)
 {
-	return JS_GetClass(cx, obj);
+	UNUSED2(cx); // unused if not JS_THREADSAFE
+
+	return JS_GET_CLASS(cx, obj);
 }
 
 void* ScriptInterface::GetPrivate(JSContext* cx, JSObject* obj)
diff --git a/source/tools/atlas/wxJS/common/apiwrap.h b/source/tools/atlas/wxJS/common/apiwrap.h
index cd89991cde..3687affb35 100644
--- a/source/tools/atlas/wxJS/common/apiwrap.h
+++ b/source/tools/atlas/wxJS/common/apiwrap.h
@@ -107,7 +107,7 @@ namespace wxjs
           }
         }
 
-         JSClass *clazz = JS_GetClass(cx, obj);
+         JSClass *clazz = JS_GET_CLASS(cx, obj);
          if ( clazz == NULL )
            return NULL;
 
@@ -116,7 +116,7 @@ namespace wxjs
            obj = JS_GetPrototype(cx, obj);
            if ( obj == NULL )
              return NULL;
-           clazz = JS_GetClass(cx, obj);
+           clazz = JS_GET_CLASS(cx, obj);
            if ( clazz == NULL )
              return NULL;
          }