diff --git a/lib/langfontfinder/__init__.py b/lib/langfontfinder/__init__.py
index d434787..78cbd95 100644
--- a/lib/langfontfinder/__init__.py
+++ b/lib/langfontfinder/__init__.py
@@ -35,6 +35,8 @@ def _getmatch(self, lng, scr, reg, var, regnum):
 
     def match(self, lng, scr, reg, var):
         """Given broken out lang tag components, return the rule result that matches."""
+        if scr is not None and len(scr) and scr not in self.scrrules[1]:
+            return None         # bail on unknown script
         res = self._getmatch(
             lng, scr, reg, var, self.scrrules[1].get(scr, self.scrrules[0])
         )
diff --git a/test/testapi b/test/testapi
index 7f88142..e3ad603 100755
--- a/test/testapi
+++ b/test/testapi
@@ -17,5 +17,17 @@ def test_lang_en():
     res = response.json()
     assert res['defaultfamily'][0] == 'charissil'
 
+def test_bad_script():
+    response = client.get("/lang/en-Fred")
+    assert response.status_code == 404
+
+def test_unknown_script():
+    response = client.get("/lang/en-Latf")
+    assert response.status_code == 200
+    res = response.json()
+    assert res['defaultfamily'][0] == ''
+
 if __name__ == "__main__":
     test_lang_en()
+    test_bad_script()
+    test_unknown_script()