diff --git a/lib/py/src/protocol/fastbinary.c b/lib/py/src/protocol/fastbinary.c
index 5625f4b..0945ca7 100644
--- a/lib/py/src/protocol/fastbinary.c
+++ b/lib/py/src/protocol/fastbinary.c
@@ -419,7 +419,7 @@
 
   case T_MAP: {
     PyObject *k, *v;
-    int pos = 0;
+    Py_ssize_t pos = 0;
     Py_ssize_t len;
 
     MapTypeArgs parsedargs;