diff --git a/featureflags_client/http/conditions.py b/featureflags_client/http/conditions.py
index 1bec2cb..2adeca9 100644
--- a/featureflags_client/http/conditions.py
+++ b/featureflags_client/http/conditions.py
@@ -17,7 +17,7 @@ def except_false(func: Callable) -> Callable:
     def wrapper(ctx: Dict[str, Any]) -> Any:
         try:
             return func(ctx)
-        except TypeError:
+        except (TypeError, ValueError):
             return False
 
     return wrapper
diff --git a/featureflags_client/tests/http/test_conditions.py b/featureflags_client/tests/http/test_conditions.py
index 287e245..4d42bb1 100644
--- a/featureflags_client/tests/http/test_conditions.py
+++ b/featureflags_client/tests/http/test_conditions.py
@@ -98,6 +98,9 @@ def test_percent():
 
     assert check_op(_UNDEFINED, percent, 100) is False
 
+    assert check_op("foo", percent, '100') is True
+    assert check_op("foo", percent, 'not_number') is False
+
 
 def test_regexp():
     assert check_op("anything", regexp, ".") is True