diff --git a/param/parameters.py b/param/parameters.py
index ed11b53b..3a12e6b5 100644
--- a/param/parameters.py
+++ b/param/parameters.py
@@ -16,15 +16,16 @@
 Parameters and Parameterized classes.
 """
 
-import numbers
-import os.path
-import sys
+import collections
 import copy
-import glob
-import re
 import datetime as dt
-import collections
+import glob
+import inspect
+import numbers
+import os.path
 import pathlib
+import re
+import sys
 import typing
 import warnings
 
@@ -803,7 +804,7 @@ def _validate_bounds(self, val, bounds, inclusive_bounds):
                     )
 
     def _validate_value(self, val, allow_None):
-        if (allow_None and val is None) or callable(val):
+        if (allow_None and val is None) or (callable(val) and not inspect.isgeneratorfunction(val)):
             return
 
         if not _is_number(val):