1 files changed, 7 insertions, 0 deletions
diff --git a/libmproxy/flow.py b/libmproxy/flow.py
index 44bb1018..8e4c2117 100644
--- a/libmproxy/flow.py
+++ b/libmproxy/flow.py
@@ -1092,7 +1092,14 @@ class Flow:
         """
             Match this flow against a compiled filter expression. Returns True
             if matched, False if not.
+
+            If f is a string, it will be compiled as a filter expression. If
+            the expression is invalid, ValueError is raised.
         """
+        if isinstance(f, basestring):
+            f = filt.parse(f)
+            if not f:
+                raise ValueError("Invalid filter expression.")
         if f:
             return f(self)
         return True