diff --git a/common.c b/common.c
index c9a825ed0ae6014e18e1120de57f67854b530d3e..b4a0b8e23b6badee81e4f1e47173382ea2d7a9be 100644
--- a/common.c
+++ b/common.c
@@ -124,7 +124,7 @@ int validate_puk_format(char *puk)
 	if (!isdigits(puk)) {
 		debug_print("Please enter digits only!\n");
 		goto fail;
-	} else if (strlen(puk) == 8) {
+	} else if (strlen(puk) != 8) {
 		debug_print("Please enter 8 digits!\n");
 		goto fail;
 	}