diff --git a/image/src/imgLoader.cpp b/image/src/imgLoader.cpp
index a96e00796d4..063cf53cfb5 100644
--- a/image/src/imgLoader.cpp
+++ b/image/src/imgLoader.cpp
@@ -1611,11 +1611,16 @@ bool imgLoader::ValidateEntry(imgCacheEntry *aEntry,
                                 aCORSMode, aLoadingPrincipal))
     return false;
 
-  // Never validate data URIs.
+  // data URIs are immutable and by their nature can't leak data, so we can
+  // just return true in that case.  Doing so would mean that shift-reload
+  // doesn't reload data URI documents/images though (which is handy for
+  // debugging during gecko development) so we make an exception in that case.
   nsAutoCString scheme;
   aURI->GetScheme(scheme);
-  if (scheme.EqualsLiteral("data"))
+  if (scheme.EqualsLiteral("data") &&
+      !(aLoadFlags & nsIRequest::LOAD_BYPASS_CACHE)) {
     return true;
+  }
 
   bool validateRequest = false;