diff --git a/layout/inspector/src/inFlasher.cpp b/layout/inspector/src/inFlasher.cpp
index deb83d37ee74..7297f887b951 100644
--- a/layout/inspector/src/inFlasher.cpp
+++ b/layout/inspector/src/inFlasher.cpp
@@ -134,6 +134,7 @@ inFlasher::SetInvert(PRBool aInvert)
 NS_IMETHODIMP
 inFlasher::RepaintElement(nsIDOMElement* aElement)
 {
+  NS_ENSURE_ARG_POINTER(aElement);
   nsCOMPtr<nsIDOMWindowInternal> window = inLayoutUtils::GetWindowFor(aElement);
   if (!window) return NS_OK;
   nsCOMPtr<nsIPresShell> presShell = inLayoutUtils::GetPresShellFor(window);
@@ -149,6 +150,7 @@ inFlasher::RepaintElement(nsIDOMElement* aElement)
 NS_IMETHODIMP 
 inFlasher::DrawElementOutline(nsIDOMElement* aElement)
 {
+  NS_ENSURE_ARG_POINTER(aElement);
   nsCOMPtr<nsIDOMWindowInternal> window = inLayoutUtils::GetWindowFor(aElement);
   if (!window) return NS_OK;
   nsCOMPtr<nsIPresShell> presShell = inLayoutUtils::GetPresShellFor(window);
@@ -183,8 +185,7 @@ inFlasher::DrawElementOutline(nsIDOMElement* aElement)
 NS_IMETHODIMP
 inFlasher::ScrollElementIntoView(nsIDOMElement *aElement)
 {
-  NS_PRECONDITION(aElement, "Dude, where's my arg?!");
-
+  NS_ENSURE_ARG_POINTER(aElement);
   nsCOMPtr<nsIDOMWindowInternal> window = inLayoutUtils::GetWindowFor(aElement);
   if (!window) {
     return NS_OK;