diff --git a/client/mifare/mfkey.c b/client/mifare/mfkey.c
index ee0c9f052..7d04762b8 100644
--- a/client/mifare/mfkey.c
+++ b/client/mifare/mfkey.c
@@ -14,7 +14,7 @@
 #include "crapto1/crapto1.h"
 
 // MIFARE
-int compare_uint64(const void *a, const void *b) {
+int inline compare_uint64(const void *a, const void *b) {
     if (*(uint64_t *)b == *(uint64_t *)a) return 0;
     if (*(uint64_t *)b < * (uint64_t *)a) return 1;
     return -1;