diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 4e81d63..d640c39 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -474,7 +474,7 @@
 
 #ifdef Py_USING_UNICODE
 
-volatile int x;
+static volatile int x;
 
 /* Test the u and u# codes for PyArg_ParseTuple. May leak memory in case
    of an error.