diff --git a/libmemtrack/memtrack_test.c b/libmemtrack/memtrack_test.c
index cd94bc5..eaadfa7 100644
--- a/libmemtrack/memtrack_test.c
+++ b/libmemtrack/memtrack_test.c
@@ -35,7 +35,7 @@
         return -1;
     }
 
-    if (asprintf(&filename, "/proc/%zd/cmdline", pid) < 0) {
+    if (asprintf(&filename, "/proc/%d/cmdline", pid) < 0) {
         rc = 1;
         goto exit;
     }