diff --git a/include/irqhandler.h b/include/irqhandler.h
index db5dd2f1..3a06d3da 100644
--- a/include/irqhandler.h
+++ b/include/irqhandler.h
@@ -17,8 +17,8 @@
 #include "timekeeper.h"
 
 void irqHandler(void *pvParameters);
-int mask_user_IRQ();
-int unmask_user_IRQ();
+void mask_user_IRQ();
+void unmask_user_IRQ();
 
 #ifdef HAS_DISPLAY
 void IRAM_ATTR DisplayIRQ();
diff --git a/src/irqhandler.cpp b/src/irqhandler.cpp
index 1ecfa59f..fabda2f2 100644
--- a/src/irqhandler.cpp
+++ b/src/irqhandler.cpp
@@ -119,19 +119,6 @@ void IRAM_ATTR GpsIRQ() {
 }
 #endif
 
-int mask_user_IRQ() {
-  if (!I2C_MUTEX_LOCK()) {
-    ESP_LOGW(TAG, "[%0.3f] i2c mutex lock failed", millis() / 1000.0);
-    return 0; // failure
-  } else {
-    xTaskNotify(irqHandlerTask, MASK_IRQ, eSetBits);
-    return 1; // success
-  }
-}
+void mask_user_IRQ() { xTaskNotify(irqHandlerTask, MASK_IRQ, eSetBits); }
 
-int unmask_user_IRQ() {
-  // end of time critical section: release I2C bus
-  I2C_MUTEX_UNLOCK();
-  xTaskNotify(irqHandlerTask, UNMASK_IRQ, eSetBits);
-  return 0;
-}
\ No newline at end of file
+void unmask_user_IRQ() { xTaskNotify(irqHandlerTask, UNMASK_IRQ, eSetBits); }
\ No newline at end of file
diff --git a/src/lorawan.cpp b/src/lorawan.cpp
index 12cae030..07d893c8 100644
--- a/src/lorawan.cpp
+++ b/src/lorawan.cpp
@@ -507,9 +507,15 @@ void IRAM_ATTR user_request_network_time_callback(void *pVoidUserUTCTime,
     return;
   }
 
-  // begin of time critical section: lock I2C bus to ensure accurate timing
-  if (!mask_user_IRQ())
-    return; // failure
+  // begin of time critical section
+
+  // lock I2C bus and application irq to ensure accurate timing
+  if (!I2C_MUTEX_LOCK()) {
+    ESP_LOGW(TAG, "[%0.3f] Timesync handshake error: i2c bus locking failed",
+             millis() / 1000.0);
+    goto finish; // failure
+  }
+  mask_user_IRQ();
 
   // Update userUTCTime, considering the difference between the GPS and UTC
   // time, and the leap seconds until year 2019
@@ -525,7 +531,9 @@ void IRAM_ATTR user_request_network_time_callback(void *pVoidUserUTCTime,
   // Update system time with time read from the network
   setMyTime(*pUserUTCTime + requestDelaySec, 0);
 
-  // end of time critical section: release I2C bus
+finish:
+  // end of time critical section: release I2C bus and app irq
+  I2C_MUTEX_UNLOCK();r
   unmask_user_IRQ();
 
 } // user_request_network_time_callback
diff --git a/src/timesync.cpp b/src/timesync.cpp
index ec85370b..00d80bcf 100644
--- a/src/timesync.cpp
+++ b/src/timesync.cpp
@@ -110,13 +110,13 @@ void process_timesync_req(void *taskparameter) {
       }
     } // end of for loop to collect timestamp samples
 
-    // begin of time critical section: lock app irq's and I2C bus
-    if (!mask_user_IRQ()) {
-      ESP_LOGW(TAG,
-               "[%0.3f] Timesync handshake error: irq masking failed",
+    // lock I2C bus and application irq to ensure accurate timing
+    if (!I2C_MUTEX_LOCK()) {
+      ESP_LOGW(TAG, "[%0.3f] Timesync handshake error: i2c bus locking failed",
                millis() / 1000.0);
       goto finish; // failure
     }
+    mask_user_IRQ();
 
     // average time offset over all collected diffs
     time_offset_ms /= TIME_SYNC_SAMPLES;
@@ -136,8 +136,10 @@ void process_timesync_req(void *taskparameter) {
     setMyTime(time_to_set, time_to_set_fraction_msec);
 
   finish:
-    // end of time critical section: release I2C bus and re-enable app irq's
+    // end of time critical section: release I2C bus and app irq
+    I2C_MUTEX_UNLOCK();
     unmask_user_IRQ();
+
     timeSyncPending = false;
 
   } // infinite while(1)