diff --git a/mozilla/string/obsolete/nsString2.h b/mozilla/string/obsolete/nsString2.h
index 7aac17c7220..3cdbeae0268 100644
--- a/mozilla/string/obsolete/nsString2.h
+++ b/mozilla/string/obsolete/nsString2.h
@@ -889,7 +889,7 @@ private:
 
 #ifdef NEW_STRING_APIS
 NS_DEF_STRING_COMPARISON_OPERATORS(nsString, PRUnichar)
-NS_DEF_DERIVED_STRING_OPERATOR_PLUS(nsAutoString, PRUnichar)
+NS_DEF_DERIVED_STRING_OPERATOR_PLUS(nsString, PRUnichar)
 #endif
 
 extern NS_COM int fputs(const nsString& aString, FILE* out);
diff --git a/mozilla/xpcom/ds/nsString2.h b/mozilla/xpcom/ds/nsString2.h
index 7aac17c7220..3cdbeae0268 100644
--- a/mozilla/xpcom/ds/nsString2.h
+++ b/mozilla/xpcom/ds/nsString2.h
@@ -889,7 +889,7 @@ private:
 
 #ifdef NEW_STRING_APIS
 NS_DEF_STRING_COMPARISON_OPERATORS(nsString, PRUnichar)
-NS_DEF_DERIVED_STRING_OPERATOR_PLUS(nsAutoString, PRUnichar)
+NS_DEF_DERIVED_STRING_OPERATOR_PLUS(nsString, PRUnichar)
 #endif
 
 extern NS_COM int fputs(const nsString& aString, FILE* out);
diff --git a/mozilla/xpcom/string/obsolete/nsString2.h b/mozilla/xpcom/string/obsolete/nsString2.h
index 7aac17c7220..3cdbeae0268 100644
--- a/mozilla/xpcom/string/obsolete/nsString2.h
+++ b/mozilla/xpcom/string/obsolete/nsString2.h
@@ -889,7 +889,7 @@ private:
 
 #ifdef NEW_STRING_APIS
 NS_DEF_STRING_COMPARISON_OPERATORS(nsString, PRUnichar)
-NS_DEF_DERIVED_STRING_OPERATOR_PLUS(nsAutoString, PRUnichar)
+NS_DEF_DERIVED_STRING_OPERATOR_PLUS(nsString, PRUnichar)
 #endif
 
 extern NS_COM int fputs(const nsString& aString, FILE* out);