diff --git a/native/jni/b64xz.c b/native/jni/b64xz.c
index bc0ee3838..4cd758410 100644
--- a/native/jni/b64xz.c
+++ b/native/jni/b64xz.c
@@ -49,7 +49,7 @@ int main(int argc, char const* argv[]) {
 
 	uint8_t in[4], buf[6144];
 	unsigned len = 0, pos = 0;
-	char c;
+	int8_t c;
 
 	xz_crc32_init();
 	struct xz_dec *dec = xz_dec_init(XZ_DYNALLOC, 1 << 26);