diff --git a/string/obsolete/nsXPIDLString.h b/string/obsolete/nsXPIDLString.h
index 294c1025b389..311c37195499 100644
--- a/string/obsolete/nsXPIDLString.h
+++ b/string/obsolete/nsXPIDLString.h
@@ -172,7 +172,7 @@ inline
 void
 nsXPIDLString::Adopt( PRUnichar* aNewValue )
   {
-    *getter_Copies(*this) = aNewValue;
+    *StartAssignmentByValue() = aNewValue;
   }
 
 // XXX THESE ARE NOT strcmp()! DON'T TRY TO USE THEM AS SUCH!
@@ -284,7 +284,7 @@ inline
 void
 nsXPIDLCString::Adopt( char* aNewValue )
   {
-    *getter_Copies(*this) = aNewValue;
+    *StartAssignmentByValue() = aNewValue;
   }
 
 // XXX THESE ARE NOT strcmp()! DON'T TRY TO USE THEM AS SUCH!
diff --git a/xpcom/string/obsolete/nsXPIDLString.h b/xpcom/string/obsolete/nsXPIDLString.h
index 294c1025b389..311c37195499 100644
--- a/xpcom/string/obsolete/nsXPIDLString.h
+++ b/xpcom/string/obsolete/nsXPIDLString.h
@@ -172,7 +172,7 @@ inline
 void
 nsXPIDLString::Adopt( PRUnichar* aNewValue )
   {
-    *getter_Copies(*this) = aNewValue;
+    *StartAssignmentByValue() = aNewValue;
   }
 
 // XXX THESE ARE NOT strcmp()! DON'T TRY TO USE THEM AS SUCH!
@@ -284,7 +284,7 @@ inline
 void
 nsXPIDLCString::Adopt( char* aNewValue )
   {
-    *getter_Copies(*this) = aNewValue;
+    *StartAssignmentByValue() = aNewValue;
   }
 
 // XXX THESE ARE NOT strcmp()! DON'T TRY TO USE THEM AS SUCH!