diff --git a/mozilla/content/html/style/src/nsHTMLAttributes.cpp b/mozilla/content/html/style/src/nsHTMLAttributes.cpp
index a476b85bcef..9aa14ca6a5d 100644
--- a/mozilla/content/html/style/src/nsHTMLAttributes.cpp
+++ b/mozilla/content/html/style/src/nsHTMLAttributes.cpp
@@ -177,6 +177,7 @@ struct nsClassList {
     : mAtom(aCopy.mAtom),
       mNext(nsnull)
   {
+    NS_ADDREF(mAtom);
     if (nsnull != aCopy.mNext) {
       mNext = new nsClassList(*(aCopy.mNext));
     }
diff --git a/mozilla/layout/html/style/src/nsHTMLAttributes.cpp b/mozilla/layout/html/style/src/nsHTMLAttributes.cpp
index a476b85bcef..9aa14ca6a5d 100644
--- a/mozilla/layout/html/style/src/nsHTMLAttributes.cpp
+++ b/mozilla/layout/html/style/src/nsHTMLAttributes.cpp
@@ -177,6 +177,7 @@ struct nsClassList {
     : mAtom(aCopy.mAtom),
       mNext(nsnull)
   {
+    NS_ADDREF(mAtom);
     if (nsnull != aCopy.mNext) {
       mNext = new nsClassList(*(aCopy.mNext));
     }