diff --git a/sktools/src/sktools/skdef.py b/sktools/src/sktools/skdef.py
index 54a7de70..5652cdbc 100644
--- a/sktools/src/sktools/skdef.py
+++ b/sktools/src/sktools/skdef.py
@@ -503,7 +503,7 @@ def fromhsd(cls, root, query):
             name = node.tag
             match = cls._PATTERN_DEFAULT.match(name)
             if not match:
-                msg = "Invalid two center interaction '{}'".name
+                msg = "Invalid two center interaction '{}'".format(name)
                 raise sc.SkgenException(msg)
             name1, name2 = match.groups()
             key = min(name1, name2), max(name1, name2)