diff --git a/dom/base/nsAttrAndChildArray.cpp b/dom/base/nsAttrAndChildArray.cpp
index e454fda31e..08be8ef0c5 100644
--- a/dom/base/nsAttrAndChildArray.cpp
+++ b/dom/base/nsAttrAndChildArray.cpp
@@ -790,7 +790,12 @@ nsAttrAndChildArray::GrowBy(uint32_t aGrowSize)
     } while (size.value() < minSize.value());
   }
   else {
-    size = 1u << mozilla::CeilingLog2(minSize.value());
+    uint32_t shift = mozilla::CeilingLog2(minSize.value());
+    if (shift >= 32) {
+      return false;
+    }
+
+    size = 1u << shift;
   }
 
   bool needToInitialize = !mImpl;