diff --git a/libs/host/CopyFile.c b/libs/host/CopyFile.c
index 23f1260..ca52565 100644
--- a/libs/host/CopyFile.c
+++ b/libs/host/CopyFile.c
@@ -137,7 +137,7 @@
                 return -1;
             }
             if (writeCount != readCount) {
-                fprintf(stderr, "acp: partial write to '%s' (%d of %d)\n",
+                fprintf(stderr, "acp: partial write to '%s' (%zd of %zd)\n",
                     dst, writeCount, readCount);
                 return -1;
             }