diff --git a/respodns/ip_util.py b/respodns/ip_util.py
index 34d96ec..931dc06 100644
--- a/respodns/ip_util.py
+++ b/respodns/ip_util.py
@@ -23,7 +23,7 @@ def read_ips(f):
 
 def addr_to_int(ip):
     match = ipv4_pattern.fullmatch(ip)
-    assert match is not None, row
+    assert match is not None, ip
     segs = list(map(int, match.group(1, 2, 3, 4)))
     assert all(0 <= seg <= 255 for seg in segs), match.group(0)
     numeric = segs[0] << 24 | segs[1] << 16 | segs[2] << 8 | segs[3]