diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index a4912c349b10..6c0547a84185 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -8808,14 +8808,14 @@ nsGlobalWindow::SetTimeoutOrInterval(nsIScriptTimeoutHandler *aHandler,
   interval = NS_MAX(aIsInterval ? 1 : 0, interval);
 
   // Make sure we don't proceed with an interval larger than our timer
-  // code can handle.
-  if (interval > PR_IntervalToMilliseconds(DOM_MAX_TIMEOUT_VALUE)) {
-    interval = PR_IntervalToMilliseconds(DOM_MAX_TIMEOUT_VALUE);
+  // code can handle. (Note: we already forced |interval| to be non-negative,
+  // so the PRUint32 cast (to avoid compiler warnings) is ok.)
+  PRUint32 maxTimeoutMs = PR_IntervalToMilliseconds(DOM_MAX_TIMEOUT_VALUE);
+  if (static_cast<PRUint32>(interval) > maxTimeoutMs) {
+    interval = maxTimeoutMs;
   }
 
   nsTimeout *timeout = new nsTimeout();
-  if (!timeout)
-    return NS_ERROR_OUT_OF_MEMORY;
 
   // Increment the timeout's reference count to represent this function's hold
   // on the timeout.