diff --git a/extensions/webservices/proxy/src/wsppropertybagwrapper.cpp b/extensions/webservices/proxy/src/wsppropertybagwrapper.cpp
index 3886cda300d1..29dfb28e2ecd 100644
--- a/extensions/webservices/proxy/src/wsppropertybagwrapper.cpp
+++ b/extensions/webservices/proxy/src/wsppropertybagwrapper.cpp
@@ -210,6 +210,10 @@ WSPPropertyBagWrapper::GetInterfaceInfo(nsIInterfaceInfo** info)
 NS_IMETHODIMP
 WSPPropertyBagWrapper::GetInterfaces(PRUint32 *count, nsIID * **array)
 {
+  if (!mIID) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
   *count = 2;
   nsIID** iids = NS_STATIC_CAST(nsIID**, nsMemory::Alloc(2 * sizeof(nsIID*)));
   if (!iids) {
diff --git a/extensions/webservices/proxy/src/wspproxy.cpp b/extensions/webservices/proxy/src/wspproxy.cpp
index 92e6d2b33c81..6b7e9921518d 100644
--- a/extensions/webservices/proxy/src/wspproxy.cpp
+++ b/extensions/webservices/proxy/src/wspproxy.cpp
@@ -1225,6 +1225,10 @@ WSPProxy::GetInterfaces(nsIScriptableInterfaces * *aInterfaces)
 NS_IMETHODIMP
 WSPProxy::GetInterfaces(PRUint32 *count, nsIID * **array)
 {
+  if (!mIID) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
   *count = 2;
   nsIID** iids = NS_STATIC_CAST(nsIID**, nsMemory::Alloc(2 * sizeof(nsIID*)));
   if (!iids) {