--- a/gfx/webrender_bindings/Moz2DImageRenderer.cpp
+++ b/gfx/webrender_bindings/Moz2DImageRenderer.cpp
@@ -84,33 +84,33 @@ static struct FontDeleteLog {
   }
 
   // Store namespace clears as font id 0, since this will never be allocated.
   void Add(WrIdNamespace aNamespace) {
     AddEntry(AsUint64(WrFontKey { aNamespace, 0 }));
   }
 
   void AddAll() {
-    AddEntry(~0);
+    AddEntry(0);
   }
 
   // Find a matching entry in the log, searching backwards starting at the newest
   // entry and finishing with the oldest entry. Returns a brief description of why
   // the font was deleted, if known.
   const char* Find(WrFontKey aKey) {
     uint64_t keyEntry = AsUint64(aKey);
     uint64_t namespaceEntry = AsUint64(WrFontKey { aKey.mNamespace, 0 });
     size_t offset = mNextEntry;
     do {
       offset = (offset + MAX_ENTRIES - 1) % MAX_ENTRIES;
       if (mEntries[offset] == keyEntry) {
         return "deleted font";
       } else if (mEntries[offset] == namespaceEntry) {
         return "cleared namespace";
-      } else if (mEntries[offset] == ~0) {
+      } else if (!mEntries[offset]) {
         return "cleared all";
       }
     } while (offset != mNextEntry);
     return "unknown font";
   }
 } sFontDeleteLog;
 
 void