diff --git a/Readme.md b/Readme.md
index a9bf4a4..5c2b3f4 100644
--- a/Readme.md
+++ b/Readme.md
@@ -1,4 +1,4 @@
-PinChangeInterrupt Library 1.2.3
+PinChangeInterrupt Library 1.2.4
 ================================
 
 ![Header Picture](header.png)
@@ -25,7 +25,7 @@ See [PCINT pin table](https://github.com/NicoHood/PinChangeInterrupt/#pinchangei
                A11 (65), A12 (66), A13 (67), A14 (68), A15 (69)
  Arduino Leonardo/Micro: 8, 9, 10, 11, 14 (MISO), 15 (SCK), 16 (MOSI)
  HoodLoader2: All (broken out 1-7) pins are usable
- Attiny 24/44/84: All pins are usable 
+ Attiny 24/44/84: All pins are usable
  Attiny 25/45/85: All pins are usable
  Attiny 13: All pins are usable
  Attiny 441/841: All pins are usable
@@ -283,6 +283,9 @@ the new PinChangeInterrupts may help you a lot.
 Version History
 ===============
 ```
+1.2.4 Release (16.04.2016)
+* Fixed Attinyx4/x5 Issue #8
+
 1.2.3 Release (24.12.2015)
 * Added Attiny441/841 support
 
diff --git a/examples/PinChangeInterrupt_Led/PinChangeInterrupt_Led.ino b/examples/PinChangeInterrupt_Led/PinChangeInterrupt_Led.ino
index 4667aa0..87e31d6 100644
--- a/examples/PinChangeInterrupt_Led/PinChangeInterrupt_Led.ino
+++ b/examples/PinChangeInterrupt_Led/PinChangeInterrupt_Led.ino
@@ -1,34 +1,34 @@
 /*
-Copyright (c) 2014-2015 NicoHood
-See the readme for credit to other people.
+  Copyright (c) 2014-2015 NicoHood
+  See the readme for credit to other people.
 
-PinChangeInterrupt_TickTock
-Demonstrates how to use the library
+  PinChangeInterrupt_TickTock
+  Demonstrates how to use the library
 
-Connect a button/cable to pin 7 and ground.
-The Led state will change if the pin state does.
+  Connect a button/cable to pin 7 and ground.
+  The Led state will change if the pin state does.
 
-PinChangeInterrupts are different than normal Interrupts.
-See readme for more information.
-Dont use Serial or delay inside interrupts!
-This library is not compatible with SoftSerial.
+  PinChangeInterrupts are different than normal Interrupts.
+  See readme for more information.
+  Dont use Serial or delay inside interrupts!
+  This library is not compatible with SoftSerial.
 
-The following pins are usable for PinChangeInterrupt:
-Arduino Uno/Nano/Mini: All pins are usable
-Arduino Mega: 10, 11, 12, 13, 50, 51, 52, 53, A8 (62), A9 (63), A10 (64),
+  The following pins are usable for PinChangeInterrupt:
+  Arduino Uno/Nano/Mini: All pins are usable
+  Arduino Mega: 10, 11, 12, 13, 50, 51, 52, 53, A8 (62), A9 (63), A10 (64),
               A11 (65), A12 (66), A13 (67), A14 (68), A15 (69)
-Arduino Leonardo/Micro: 8, 9, 10, 11, 14 (MISO), 15 (SCK), 16 (MOSI)
-HoodLoader2: All (broken out 1-7) pins are usable
-Attiny 24/44/84: All pins are usable
-Attiny 25/45/85: All pins are usable
-Attiny 13: All pins are usable
-Attiny 441/841: All pins are usable
-ATmega644P/ATmega1284P: All pins are usable
+  Arduino Leonardo/Micro: 8, 9, 10, 11, 14 (MISO), 15 (SCK), 16 (MOSI)
+  HoodLoader2: All (broken out 1-7) pins are usable
+  Attiny 24/44/84: All pins are usable
+  Attiny 25/45/85: All pins are usable
+  Attiny 13: All pins are usable
+  Attiny 441/841: All pins are usable
+  ATmega644P/ATmega1284P: All pins are usable
 */
 
 #include "PinChangeInterrupt.h"
 
-// choose a valid PinChangeInterrupt pin of your Arduino board
+// Choose a valid PinChangeInterrupt pin of your Arduino board
 #define pinBlink 7
 
 void setup() {
@@ -36,15 +36,15 @@ void setup() {
   pinMode(pinBlink, INPUT_PULLUP);
   pinMode(LED_BUILTIN, OUTPUT);
 
-  // attach the new PinChangeInterrupt and enable event function below
+  // Attach the new PinChangeInterrupt and enable event function below
   attachPCINT(digitalPinToPCINT(pinBlink), blinkLed, CHANGE);
 }
 
 void blinkLed(void) {
-  // switch Led state
+  // Switch Led state
   digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
 }
 
 void loop() {
-  // nothing to do here
+  // Nothing to do here
 }
diff --git a/library.properties b/library.properties
index 087273c..fddfd27 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=PinChangeInterrupt
-version=1.2.3
+version=1.2.4
 author=NicoHood
 maintainer=NicoHood <blog@NicoHood.de>
 sentence=A simple & compact PinChangeInterrupt library for Arduino.
diff --git a/src/PinChangeInterrupt.cpp b/src/PinChangeInterrupt.cpp
index 44ce0fe..05f5207 100644
--- a/src/PinChangeInterrupt.cpp
+++ b/src/PinChangeInterrupt.cpp
@@ -123,7 +123,34 @@ void enablePinChangeInterruptHelper(const uint8_t pcintPort, const uint8_t pcint
 
 	// Pin change mask registers decide which pins are ENABLE as triggers
 #ifdef PCMSK0
-	*(&PCMSK0 + pcintPort) |= pcintMask;
+#ifdef PCMSK1
+	// Special case for Attinyx4 where PCMSK1 and PCMSK0 are not next to each other
+	if(&PCMSK1 - &PCMSK0 == 1){
+#endif
+		*(&PCMSK0 + pcintPort) |= pcintMask;
+#ifdef PCMSK1
+	}
+	else{
+		switch(pcintPort){
+			case 0:
+				PCMSK0 |= pcintMask;
+			break;
+			case 1:
+				PCMSK1 |= pcintMask;
+			break;
+#ifdef PCMSK2
+			case 2:
+				PCMSK2 |= pcintMask;
+			break;
+#endif
+#ifdef PCMSK3
+			case 3:
+				PCMSK3 |= pcintMask;
+			break;
+#endif
+		}
+	}
+#endif
 #elif defined(PCMSK)
 	*(&PCMSK + pcintPort) |= pcintMask;
 #endif
@@ -141,19 +168,71 @@ void enablePinChangeInterruptHelper(const uint8_t pcintPort, const uint8_t pcint
 }
 
 void disablePinChangeInterruptHelper(const uint8_t pcintPort, const uint8_t pcintMask) {
+	bool disable = false;
 #ifdef PCMSK0
-	// disable the mask.
-	*(&PCMSK0 + pcintPort) &= ~pcintMask;
+#ifdef PCMSK1
+	// Special case for Attinyx4 where PCMSK1 and PCMSK0 are not next to each other
+	if(&PCMSK1 - &PCMSK0 == 1){
+#endif
+		// disable the mask.
+		*(&PCMSK0 + pcintPort) &= ~pcintMask;
 
-	// if that's the last one, disable the interrupt.
-	if (*(&PCMSK0 + pcintPort) == 0)
+		// if that's the last one, disable the interrupt.
+		if (*(&PCMSK0 + pcintPort) == 0)
+			disable = true;
+#ifdef PCMSK1
+	}
+	else{
+		switch(pcintPort){
+			case 0:
+				// disable the mask.
+				PCMSK0 &= ~pcintMask;
+
+				// if that's the last one, disable the interrupt.
+				if (!PCMSK0)
+					disable = true;
+			break;
+			case 1:
+				// disable the mask.
+				PCMSK1 &= ~pcintMask;
+
+				// if that's the last one, disable the interrupt.
+				if (!PCMSK1)
+					disable = true;
+			break;
+#ifdef PCMSK2
+			case 2:
+				// disable the mask.
+				PCMSK2 &= ~pcintMask;
+
+				// if that's the last one, disable the interrupt.
+				if (!PCMSK2)
+					disable = true;
+			break;
+#endif
+#ifdef PCMSK3
+			case 3:
+				// disable the mask.
+				PCMSK3 &= ~pcintMask;
+
+				// if that's the last one, disable the interrupt.
+				if (!PCMSK3)
+					disable = true;
+			break;
+#endif
+		}
+	}
+#endif
 #elif defined(PCMSK)
 	// disable the mask.
 	*(&PCMSK + pcintPort) &= ~pcintMask;
 
 	// if that's the last one, disable the interrupt.
 	if (*(&PCMSK + pcintPort) == 0)
+		disable = true;
 #endif
+	if(disable)
+	{
 #ifdef PCICR
 		PCICR &= ~(1  << (pcintPort + PCIE0));
 #elif defined(GIMSK) && defined(PCIE0) /* e.g. ATtiny X4 */
@@ -163,6 +242,7 @@ void disablePinChangeInterruptHelper(const uint8_t pcintPort, const uint8_t pcin
 #else
 #error MCU has no such a register
 #endif
+	}
 }
 
 /*
diff --git a/src/PinChangeInterrupt.h b/src/PinChangeInterrupt.h
index d05be7f..98e887f 100644
--- a/src/PinChangeInterrupt.h
+++ b/src/PinChangeInterrupt.h
@@ -25,7 +25,7 @@ THE SOFTWARE.
 #pragma once
 
 // software version
-#define PCINT_VERSION 123
+#define PCINT_VERSION 124
 
 #include "Arduino.h"
 
@@ -78,7 +78,13 @@ PinChangeInterruptEventPCINT ## pcint PCINT_MACRO_BRACKETS
 
 // convert a normal pin to its PCINT number (0 - max 23), used by the user
 // calculates the pin by the Arduino definitions
-#define digitalPinToPinChangeInterrupt(p) (digitalPinToPCICR(p) ? ((8 * digitalPinToPCICRbit(p)) + digitalPinToPCMSKbit(p)) : NOT_AN_INTERRUPT)
+#if defined(PCIE0)
+#define digitalPinToPinChangeInterrupt(p) (digitalPinToPCICR(p) ? ((8 * (digitalPinToPCICRbit(p) - PCIE0)) + digitalPinToPCMSKbit(p)) : NOT_AN_INTERRUPT)
+#elif defined(PCIE)
+#define digitalPinToPinChangeInterrupt(p) (digitalPinToPCICR(p) ? ((8 * (digitalPinToPCICRbit(p) - PCIE)) + digitalPinToPCMSKbit(p)) : NOT_AN_INTERRUPT)
+#else
+#error MCU has no such a register
+#endif
 
 // alias for shorter writing
 #define PCINTEvent(n) PinChangeInterruptEvent_Wrapper(n)
diff --git a/src/PinChangeInterruptSettings.h b/src/PinChangeInterruptSettings.h
index 190c9d2..d81c67c 100644
--- a/src/PinChangeInterruptSettings.h
+++ b/src/PinChangeInterruptSettings.h
@@ -216,8 +216,8 @@ The order is also okay. */
 
 #if defined(__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
 // Port1 is connected to reset, crystal and Pin Interrupt 0
-// deactivate it by default
-#if defined(PCINT_ENABLE_PCINT1)
-#undef PCINT_ENABLE_PCINT1
+// Deactivate it by default
+#if defined(PCINT_ENABLE_PORT1)
+#undef PCINT_ENABLE_PORT1
 #endif
 #endif