diff --git a/hgext/convert/common.py b/hgext/convert/common.py
--- a/hgext/convert/common.py
+++ b/hgext/convert/common.py
@@ -459,7 +459,7 @@
         # POSIX requires at least 4096 bytes for ARG_MAX
         argmax = 4096
         try:
-            argmax = os.sysconf("SC_ARG_MAX")
+            argmax = os.sysconf(r"SC_ARG_MAX")
         except (AttributeError, ValueError):
             pass