diff --git a/Source/portable/GCC/ARM_CM3/port.c b/Source/portable/GCC/ARM_CM3/port.c
index 146efa7ea..c9f317d34 100644
--- a/Source/portable/GCC/ARM_CM3/port.c
+++ b/Source/portable/GCC/ARM_CM3/port.c
@@ -115,6 +115,7 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 {
 	/* Simulate the stack frame as it would be created by a context switch
 	interrupt. */
+	pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
 	*pxTopOfStack = portINITIAL_XPSR;	/* xPSR */
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
diff --git a/Source/portable/GCC/ARM_CM3_MPU/port.c b/Source/portable/GCC/ARM_CM3_MPU/port.c
index 859fc5b83..7b2d7254a 100644
--- a/Source/portable/GCC/ARM_CM3_MPU/port.c
+++ b/Source/portable/GCC/ARM_CM3_MPU/port.c
@@ -164,6 +164,7 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 {
 	/* Simulate the stack frame as it would be created by a context switch
 	interrupt. */
+	pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
 	*pxTopOfStack = portINITIAL_XPSR;	/* xPSR */
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
diff --git a/Source/portable/IAR/ARM_CM3/port.c b/Source/portable/IAR/ARM_CM3/port.c
index ff794e4b3..e2ce7fca1 100644
--- a/Source/portable/IAR/ARM_CM3/port.c
+++ b/Source/portable/IAR/ARM_CM3/port.c
@@ -116,6 +116,7 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 {
 	/* Simulate the stack frame as it would be created by a context switch
 	interrupt. */
+	pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
 	*pxTopOfStack = portINITIAL_XPSR;	/* xPSR */
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */
diff --git a/Source/portable/RVDS/ARM_CM3/port.c b/Source/portable/RVDS/ARM_CM3/port.c
index 6bee97c46..11e7d1874 100644
--- a/Source/portable/RVDS/ARM_CM3/port.c
+++ b/Source/portable/RVDS/ARM_CM3/port.c
@@ -108,6 +108,7 @@ portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE
 {
 	/* Simulate the stack frame as it would be created by a context switch
 	interrupt. */
+	pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
 	*pxTopOfStack = portINITIAL_XPSR;	/* xPSR */
 	pxTopOfStack--;
 	*pxTopOfStack = ( portSTACK_TYPE ) pxCode;	/* PC */