diff --git a/os/ports/GCC/ARMCMx/chcore_v6m.h b/os/ports/GCC/ARMCMx/chcore_v6m.h
index 644f73d79..84005f162 100644
--- a/os/ports/GCC/ARMCMx/chcore_v6m.h
+++ b/os/ports/GCC/ARMCMx/chcore_v6m.h
@@ -66,15 +66,13 @@
  * @brief   Per-thread stack overhead for interrupts servicing.
  * @details This constant is used in the calculation of the correct working
  *          area size.
- *          This value can be zero on those architecture where there is a
- *          separate interrupt stack and the stack space between @p intctx and
- *          @p extctx is known to be zero.
- * @note    In this port it is conservatively set to 16 because the function
- *          @p chSchDoReschedule() can have a stack frame, especially with
- *          compiler optimizations disabled.
+ * @note    In this port this value is conservatively set to 32 because the
+ *          function @p chSchDoReschedule() can have a stack frame, especially
+ *          with compiler optimizations disabled. The value can be reduced
+ *          when compiler optimizations are enabled.
  */
 #if !defined(PORT_INT_REQUIRED_STACK)
-#define PORT_INT_REQUIRED_STACK         16
+#define PORT_INT_REQUIRED_STACK         32
 #endif
 
 /**
diff --git a/os/ports/GCC/ARMCMx/chcore_v7m.h b/os/ports/GCC/ARMCMx/chcore_v7m.h
index 407b6b571..10edcc45b 100644
--- a/os/ports/GCC/ARMCMx/chcore_v7m.h
+++ b/os/ports/GCC/ARMCMx/chcore_v7m.h
@@ -63,15 +63,13 @@
  * @brief   Per-thread stack overhead for interrupts servicing.
  * @details This constant is used in the calculation of the correct working
  *          area size.
- *          This value can be zero on those architecture where there is a
- *          separate interrupt stack and the stack space between @p intctx and
- *          @p extctx is known to be zero.
- * @note    In this port it is conservatively set to 16 because the function
- *          @p chSchDoReschedule() can have a stack frame, especially with
- *          compiler optimizations disabled.
+ * @note    In this port this value is conservatively set to 32 because the
+ *          function @p chSchDoReschedule() can have a stack frame, especially
+ *          with compiler optimizations disabled. The value can be reduced
+ *          when compiler optimizations are enabled.
  */
 #if !defined(PORT_INT_REQUIRED_STACK)
-#define PORT_INT_REQUIRED_STACK         16
+#define PORT_INT_REQUIRED_STACK         32
 #endif
 
 /**
diff --git a/os/ports/IAR/ARMCMx/chcore_v6m.h b/os/ports/IAR/ARMCMx/chcore_v6m.h
index 9087f3dd8..8a2ef48e5 100644
--- a/os/ports/IAR/ARMCMx/chcore_v6m.h
+++ b/os/ports/IAR/ARMCMx/chcore_v6m.h
@@ -66,15 +66,13 @@
  * @brief   Per-thread stack overhead for interrupts servicing.
  * @details This constant is used in the calculation of the correct working
  *          area size.
- *          This value can be zero on those architecture where there is a
- *          separate interrupt stack and the stack space between @p intctx and
- *          @p extctx is known to be zero.
- * @note    In this port it is conservatively set to 16 because the function
- *          @p chSchDoReschedule() can have a stack frame, especially with
- *          compiler optimizations disabled.
+ * @note    In this port this value is conservatively set to 32 because the
+ *          function @p chSchDoReschedule() can have a stack frame, especially
+ *          with compiler optimizations disabled. The value can be reduced
+ *          when compiler optimizations are enabled.
  */
 #if !defined(PORT_INT_REQUIRED_STACK)
-#define PORT_INT_REQUIRED_STACK         16
+#define PORT_INT_REQUIRED_STACK         32
 #endif
 
 /**
diff --git a/os/ports/IAR/ARMCMx/chcore_v7m.h b/os/ports/IAR/ARMCMx/chcore_v7m.h
index 8615eaab6..b46ef22f0 100644
--- a/os/ports/IAR/ARMCMx/chcore_v7m.h
+++ b/os/ports/IAR/ARMCMx/chcore_v7m.h
@@ -63,15 +63,13 @@
  * @brief   Per-thread stack overhead for interrupts servicing.
  * @details This constant is used in the calculation of the correct working
  *          area size.
- *          This value can be zero on those architecture where there is a
- *          separate interrupt stack and the stack space between @p intctx and
- *          @p extctx is known to be zero.
- * @note    In this port it is conservatively set to 16 because the function
- *          @p chSchDoReschedule() can have a stack frame, especially with
- *          compiler optimizations disabled.
+ * @note    In this port this value is conservatively set to 32 because the
+ *          function @p chSchDoReschedule() can have a stack frame, especially
+ *          with compiler optimizations disabled. The value can be reduced
+ *          when compiler optimizations are enabled.
  */
 #if !defined(PORT_INT_REQUIRED_STACK)
-#define PORT_INT_REQUIRED_STACK         16
+#define PORT_INT_REQUIRED_STACK         32
 #endif
 
 /**
diff --git a/os/ports/RVCT/ARMCMx/chcore_v6m.h b/os/ports/RVCT/ARMCMx/chcore_v6m.h
index 89ab92640..5de576a21 100644
--- a/os/ports/RVCT/ARMCMx/chcore_v6m.h
+++ b/os/ports/RVCT/ARMCMx/chcore_v6m.h
@@ -66,15 +66,13 @@
  * @brief   Per-thread stack overhead for interrupts servicing.
  * @details This constant is used in the calculation of the correct working
  *          area size.
- *          This value can be zero on those architecture where there is a
- *          separate interrupt stack and the stack space between @p intctx and
- *          @p extctx is known to be zero.
- * @note    In this port it is conservatively set to 16 because the function
- *          @p chSchDoReschedule() can have a stack frame, especially with
- *          compiler optimizations disabled.
+ * @note    In this port this value is conservatively set to 32 because the
+ *          function @p chSchDoReschedule() can have a stack frame, especially
+ *          with compiler optimizations disabled. The value can be reduced
+ *          when compiler optimizations are enabled.
  */
 #if !defined(PORT_INT_REQUIRED_STACK)
-#define PORT_INT_REQUIRED_STACK         16
+#define PORT_INT_REQUIRED_STACK         32
 #endif
 
 /**
diff --git a/os/ports/RVCT/ARMCMx/chcore_v7m.h b/os/ports/RVCT/ARMCMx/chcore_v7m.h
index b568d5e5a..98bbb6358 100644
--- a/os/ports/RVCT/ARMCMx/chcore_v7m.h
+++ b/os/ports/RVCT/ARMCMx/chcore_v7m.h
@@ -63,15 +63,13 @@
  * @brief   Per-thread stack overhead for interrupts servicing.
  * @details This constant is used in the calculation of the correct working
  *          area size.
- *          This value can be zero on those architecture where there is a
- *          separate interrupt stack and the stack space between @p intctx and
- *          @p extctx is known to be zero.
- * @note    In this port it is conservatively set to 16 because the function
- *          @p chSchDoReschedule() can have a stack frame, especially with
- *          compiler optimizations disabled.
+ * @note    In this port this value is conservatively set to 32 because the
+ *          function @p chSchDoReschedule() can have a stack frame, especially
+ *          with compiler optimizations disabled. The value can be reduced
+ *          when compiler optimizations are enabled.
  */
 #if !defined(PORT_INT_REQUIRED_STACK)
-#define PORT_INT_REQUIRED_STACK         16
+#define PORT_INT_REQUIRED_STACK         32
 #endif
 
 /**
diff --git a/readme.txt b/readme.txt
index 33cfe3cdb..28a3bd26d 100644
--- a/readme.txt
+++ b/readme.txt
@@ -135,6 +135,11 @@
   lwIP demos.
 - NEW: lwIP related code is not centralized into a single place, no need to
   duplicate the code in each application or demo.
+- CHANGE: The PORT_INT_REQUIRED_STACK parameter for the Cortex-Mx ports has
+  been increased to 32 from 16 because the stack frame sizes are increased
+  when compiling with optimizations disabled, which is common during
+  debugging. In order to save RAM trim back this value when compilung with
+  optimizations enabled.
 - CHANGE: Macros icuGetWidthI() and icuGetPeriodI() renamed to  icuGetWidth()
   and icuGetPeriod().
 - CHANGE: Renamed Ethernet driver in AT91 HAL ETHD1.