diff --git a/NmraDcc.cpp b/NmraDcc.cpp
index fa2561a..4034f53 100644
--- a/NmraDcc.cpp
+++ b/NmraDcc.cpp
@@ -342,9 +342,9 @@ void ExternalInterruptHandler(void)
 // Bit evaluation without Timer 0 ------------------------------
     uint8_t DccBitVal;
     static int8_t  bit1, bit2 ;
-    static unsigned long  lastMicros = 0;
+    static word  lastMicros = 0;
     static byte halfBit, DCC_IrqRunning;
-    unsigned long  actMicros, bitMicros;
+    unsigned int  actMicros, bitMicros;
     if ( DCC_IrqRunning ) {
         // nested DCC IRQ - obviously there are glitches
         // ignore this interrupt and increment glitchcounter