diff --git a/bilby/core/utils.py b/bilby/core/utils.py
index 3b590215545dbcbe1adade632a05712b8d1f6091..77d8b0c90b229f5400f3c045ab876c57e09b66b6 100644
--- a/bilby/core/utils.py
+++ b/bilby/core/utils.py
@@ -1250,7 +1250,7 @@ def get_function_path(func):
 
 
 def loaded_modules_dict():
-    module_names = sys.modules.keys()
+    module_names = list(sys.modules.keys())
     vdict = {}
     for key in module_names:
         if "." not in key: