diff --git a/pcsc-relay/src/pcsc.c b/pcsc-relay/src/pcsc.c
index 62cabdc..c4a8c65 100644
--- a/pcsc-relay/src/pcsc.c
+++ b/pcsc-relay/src/pcsc.c
@@ -128,7 +128,7 @@ static int pcsc_connect(driver_data_t **driver_data)
         RELAY_ERROR("Could not connect to %s\n", reader);
         goto err;
     }
-    INFO("Connected to reader %u: %s\n", i, reader);
+    INFO("Connected to reader %zu: %s\n", i, reader);
     hexdump("Card's ATR: ", state.rgbAtr, state.cbAtr);
 
 err: