diff --git a/cores/arduino/wiring_pulse.c b/cores/arduino/wiring_pulse.c
index 0157114..8f232f1 100755
--- a/cores/arduino/wiring_pulse.c
+++ b/cores/arduino/wiring_pulse.c
@@ -44,6 +44,11 @@ unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout)
 	unsigned long numloops = 0;
 	unsigned long maxloops = microsecondsToClockCycles(timeout) / 16;
 	
+	// wait for any previous pulse to end
+	while ((*portInputRegister(port) & bit) == stateMask)
+		if (numloops++ == maxloops)
+			return 0;
+	
 	// wait for the pulse to start
 	while ((*portInputRegister(port) & bit) != stateMask)
 		if (numloops++ == maxloops)