diff --git a/mozilla/string/obsolete/nsString.h b/mozilla/string/obsolete/nsString.h
index 0f6d884fe86..f3dda1b5ce2 100644
--- a/mozilla/string/obsolete/nsString.h
+++ b/mozilla/string/obsolete/nsString.h
@@ -495,6 +495,7 @@ private:
 };
 
 // NS_DEF_STRING_COMPARISON_OPERATORS(nsCString, char)
+NS_DEF_DERIVED_STRING_OPERATOR_PLUS(nsCString, char)
 
 extern NS_COM int fputs(const nsCString& aString, FILE* out);
 //ostream& operator<<(ostream& aStream,const nsCString& aString);
diff --git a/mozilla/string/obsolete/nsString2.h b/mozilla/string/obsolete/nsString2.h
index 6b9b906618d..7baa4e5d08c 100644
--- a/mozilla/string/obsolete/nsString2.h
+++ b/mozilla/string/obsolete/nsString2.h
@@ -571,6 +571,7 @@ private:
 };
 
 // NS_DEF_STRING_COMPARISON_OPERATORS(nsString, PRUnichar)
+NS_DEF_DERIVED_STRING_OPERATOR_PLUS(nsString, PRUnichar)
 
 extern NS_COM int fputs(const nsString& aString, FILE* out);
 //ostream& operator<<(ostream& aStream,const nsString& aString);
diff --git a/mozilla/xpcom/ds/nsString.h b/mozilla/xpcom/ds/nsString.h
index 0f6d884fe86..f3dda1b5ce2 100644
--- a/mozilla/xpcom/ds/nsString.h
+++ b/mozilla/xpcom/ds/nsString.h
@@ -495,6 +495,7 @@ private:
 };
 
 // NS_DEF_STRING_COMPARISON_OPERATORS(nsCString, char)
+NS_DEF_DERIVED_STRING_OPERATOR_PLUS(nsCString, char)
 
 extern NS_COM int fputs(const nsCString& aString, FILE* out);
 //ostream& operator<<(ostream& aStream,const nsCString& aString);
diff --git a/mozilla/xpcom/ds/nsString2.h b/mozilla/xpcom/ds/nsString2.h
index 6b9b906618d..7baa4e5d08c 100644
--- a/mozilla/xpcom/ds/nsString2.h
+++ b/mozilla/xpcom/ds/nsString2.h
@@ -571,6 +571,7 @@ private:
 };
 
 // NS_DEF_STRING_COMPARISON_OPERATORS(nsString, PRUnichar)
+NS_DEF_DERIVED_STRING_OPERATOR_PLUS(nsString, PRUnichar)
 
 extern NS_COM int fputs(const nsString& aString, FILE* out);
 //ostream& operator<<(ostream& aStream,const nsString& aString);
diff --git a/mozilla/xpcom/string/obsolete/nsString.h b/mozilla/xpcom/string/obsolete/nsString.h
index 0f6d884fe86..f3dda1b5ce2 100644
--- a/mozilla/xpcom/string/obsolete/nsString.h
+++ b/mozilla/xpcom/string/obsolete/nsString.h
@@ -495,6 +495,7 @@ private:
 };
 
 // NS_DEF_STRING_COMPARISON_OPERATORS(nsCString, char)
+NS_DEF_DERIVED_STRING_OPERATOR_PLUS(nsCString, char)
 
 extern NS_COM int fputs(const nsCString& aString, FILE* out);
 //ostream& operator<<(ostream& aStream,const nsCString& aString);
diff --git a/mozilla/xpcom/string/obsolete/nsString2.h b/mozilla/xpcom/string/obsolete/nsString2.h
index 6b9b906618d..7baa4e5d08c 100644
--- a/mozilla/xpcom/string/obsolete/nsString2.h
+++ b/mozilla/xpcom/string/obsolete/nsString2.h
@@ -571,6 +571,7 @@ private:
 };
 
 // NS_DEF_STRING_COMPARISON_OPERATORS(nsString, PRUnichar)
+NS_DEF_DERIVED_STRING_OPERATOR_PLUS(nsString, PRUnichar)
 
 extern NS_COM int fputs(const nsString& aString, FILE* out);
 //ostream& operator<<(ostream& aStream,const nsString& aString);