diff --git a/mcutils.py b/mcutils.py
index 8a25810..7972ca9 100644
--- a/mcutils.py
+++ b/mcutils.py
@@ -1072,7 +1072,7 @@ def iminuitClass(modelFunc):
 def iminuitParsToStr(iminuit,withErrs=True,withFixed=True):
   values = iminuit.values
   errs   = iminuit.errors
-  pnames = values.keys()
+  pnames = list(values.keys())
   lenParNames = max( [len(p) for p in pnames] )
   fmt = "%%%ds" % lenParNames
   pnames.sort()