diff --git a/src/ILAMB/ModelResult.py b/src/ILAMB/ModelResult.py
index 7038b648..44fd8cf4 100644
--- a/src/ILAMB/ModelResult.py
+++ b/src/ILAMB/ModelResult.py
@@ -135,7 +135,7 @@ def _get(key, dset):
                         continue
                     if self.filter not in fileName:
                         continue
-                    if self.regex is not "":
+                    if self.regex != "":
                         m = re.search(self.regex, fileName)
                         if not m:
                             continue