diff --git a/src/DataTree.hh b/src/DataTree.hh
index adbd717e64cf19ac6f0ac6df75a8e363f2c72084..fca1ec6a3eebf3a06fb555ab7fd53f22fb44060d 100644
--- a/src/DataTree.hh
+++ b/src/DataTree.hh
@@ -153,7 +153,7 @@ public:
   {
   public:
     string name;
-    LocalVariableException(str name_arg) : name(name_arg) {}
+    LocalVariableException(string name_arg) : name(name_arg) {}
   };
 
   class DivisionByZeroException