diff --git a/src/DataTree.hh b/src/DataTree.hh
index c0ad2ec9ea6fddfbc1f4e727543b5b96b115fd63..5800dba6c9bb934d674e1124bfdea69ccaea6ba2 100644
--- a/src/DataTree.hh
+++ b/src/DataTree.hh
@@ -146,7 +146,7 @@ public:
   {
   public:
     string name;
-    LocalVariableException(str name_arg) : name(name_arg) {}
+    LocalVariableException(string name_arg) : name(name_arg) {}
   };
 
   class DivisionByZeroException