diff --git a/src/mfoc.c b/src/mfoc.c
index bde3b23..a9adfc1 100644
--- a/src/mfoc.c
+++ b/src/mfoc.c
@@ -676,7 +676,8 @@ int mf_enhanced_auth(int e_sector, int a_sector, mftag t, mfreader r, denonce *d
 
   uint32_t Nt, NtLast, NtProbe, NtEnc, Ks1;
 
-  int i, m;
+  int i;
+  uint32_t m;
 
   // Prepare AUTH command
   Auth[0] = (t.sectors[e_sector].foundKeyA) ? MC_AUTH_A : MC_AUTH_B;
diff --git a/src/mfoc.h b/src/mfoc.h
index db16c0f..157b28a 100644
--- a/src/mfoc.h
+++ b/src/mfoc.h
@@ -56,7 +56,7 @@ typedef struct {
 
 typedef struct {
   uint64_t        *brokenKeys;
-  int32_t         size;
+  uint32_t         size;
 } bKeys;
 
 typedef struct {