diff --git a/armsrc/iso14443a.c b/armsrc/iso14443a.c
index db347cf13..38eb2ecb6 100644
--- a/armsrc/iso14443a.c
+++ b/armsrc/iso14443a.c
@@ -2044,7 +2044,7 @@ bool GetIso14443aAnswerFromTag_Thinfilm(uint8_t *receivedResponse,  uint8_t *rec
             }
         }
 
-        if (GetTickCount() - receive_timer >  100)
+        if (GetTickCountDelta(receive_timer) >  100)
             break;
     }
     *received_len = Demod.len;
@@ -2094,7 +2094,7 @@ static int GetIso14443aAnswerFromTag(uint8_t *receivedResponse, uint8_t *receive
         }
 
         // timeout already in ms + 100ms guard time
-        if (GetTickCount() - receive_timer > timeout + 100)
+        if (GetTickCountDelta(receive_timer) > timeout + 100)
             break;
     }
     return false;
diff --git a/armsrc/mifaresim.c b/armsrc/mifaresim.c
index 0f912c083..cdd8b556d 100644
--- a/armsrc/mifaresim.c
+++ b/armsrc/mifaresim.c
@@ -1106,7 +1106,7 @@ void Mifare1ksim(uint16_t flags, uint8_t exitAfterNReads, uint8_t *datain, uint1
                     Dbprintf("[MFEMUL_AUTH1] AUTH COMPLETED for sector %d with key %c. time=%d",
                              cardAUTHSC,
                              cardAUTHKEY == 0 ? 'A' : 'B',
-                             GetTickCount() - authTimer
+                             GetTickCountDelta(authTimer)
                             );
                 }
                 LED_C_ON();