--- a/netwerk/base/Predictor.cpp
+++ b/netwerk/base/Predictor.cpp
@@ -2427,16 +2427,26 @@ Predictor::UpdateCacheability(nsIURI *so
 {
   MOZ_ASSERT(NS_IsMainThread());
 
   if (lci && lci->IsPrivate()) {
     PREDICTOR_LOG(("Predictor::UpdateCacheability in PB mode - ignoring"));
     return;
   }
 
+  if (!sourceURI || !targetURI) {
+    PREDICTOR_LOG(("Predictor::UpdateCacheability missing source or target uri"));
+    return;
+  }
+
+  if (!IsNullOrHttp(sourceURI) || !IsNullOrHttp(targetURI)) {
+    PREDICTOR_LOG(("Predictor::UpdateCacheability non-http(s) uri"));
+    return;
+  }
+
   RefPtr<Predictor> self = sSelf;
   if (self) {
     nsAutoCString method;
     requestHead.Method(method);
     self->UpdateCacheabilityInternal(sourceURI, targetURI, httpStatus,
                                      method);
   }
 }