diff --git a/demos/ARMCM0-LPC1114-GCC/Makefile b/demos/ARMCM0-LPC1114-GCC/Makefile
index 544c58679..5c481ec20 100644
--- a/demos/ARMCM0-LPC1114-GCC/Makefile
+++ b/demos/ARMCM0-LPC1114-GCC/Makefile
@@ -5,7 +5,7 @@
 
 # Compiler options here.
 ifeq ($(USE_OPT),)
-  USE_OPT = -O2 -ggdb -fomit-frame-pointer -mabi=apcs-gnu
+  USE_OPT = -O2 -ggdb -fomit-frame-pointer
 endif
 
 # C++ specific options here (added to USE_OPT).
diff --git a/demos/ARMCM3-LPC1343-GCC/Makefile b/demos/ARMCM3-LPC1343-GCC/Makefile
index d85428b16..0bc5276b4 100644
--- a/demos/ARMCM3-LPC1343-GCC/Makefile
+++ b/demos/ARMCM3-LPC1343-GCC/Makefile
@@ -5,7 +5,7 @@
 
 # Compiler options here.
 ifeq ($(USE_OPT),)
-  USE_OPT = -O2 -ggdb -fomit-frame-pointer -mabi=apcs-gnu
+  USE_OPT = -O2 -ggdb -fomit-frame-pointer
 endif
 
 # C++ specific options here (added to USE_OPT).
diff --git a/demos/ARMCM3-STM32F103-FATFS-GCC/Makefile b/demos/ARMCM3-STM32F103-FATFS-GCC/Makefile
index a1c7a5668..8926ccbfc 100644
--- a/demos/ARMCM3-STM32F103-FATFS-GCC/Makefile
+++ b/demos/ARMCM3-STM32F103-FATFS-GCC/Makefile
@@ -5,7 +5,7 @@
 
 # Compiler options here.
 ifeq ($(USE_OPT),)
-  USE_OPT = -O2 -ggdb -fomit-frame-pointer -mabi=apcs-gnu -falign-functions=16
+  USE_OPT = -O2 -ggdb -fomit-frame-pointer -falign-functions=16
 endif
 
 # C++ specific options here (added to USE_OPT).
diff --git a/demos/ARMCM3-STM32F103-GCC/Makefile b/demos/ARMCM3-STM32F103-GCC/Makefile
index 623ddc8ee..bf9247aba 100644
--- a/demos/ARMCM3-STM32F103-GCC/Makefile
+++ b/demos/ARMCM3-STM32F103-GCC/Makefile
@@ -5,7 +5,7 @@
 
 # Compiler options here.
 ifeq ($(USE_OPT),)
-  USE_OPT = -O2 -ggdb -fomit-frame-pointer -mabi=apcs-gnu -falign-functions=16
+  USE_OPT = -O2 -ggdb -fomit-frame-pointer -falign-functions=16
 endif
 
 # C++ specific options here (added to USE_OPT).
diff --git a/demos/ARMCM3-STM32F107-GCC/Makefile b/demos/ARMCM3-STM32F107-GCC/Makefile
index f8767cfdf..c199576c6 100644
--- a/demos/ARMCM3-STM32F107-GCC/Makefile
+++ b/demos/ARMCM3-STM32F107-GCC/Makefile
@@ -5,7 +5,7 @@
 
 # Compiler options here.
 ifeq ($(USE_OPT),)
-  USE_OPT = -O2 -ggdb -fomit-frame-pointer -mabi=apcs-gnu -falign-functions=16
+  USE_OPT = -O2 -ggdb -fomit-frame-pointer -falign-functions=16
 endif
 
 # C++ specific options here (added to USE_OPT).
diff --git a/readme.txt b/readme.txt
index e5e5bf5b9..ead483415 100644
--- a/readme.txt
+++ b/readme.txt
@@ -68,6 +68,10 @@
   Cortex-Mx port (bug 3025133).
 - NEW: Added friendly interrupt vectors names to the STM32 HAL (change request
   3023944).
+- CHANGE: Removed the option -mabi=apcs-gnu from all the Cortex-Mx demos. The
+  option is not compatible with the 64 bits stack alignment now default in
+  the Cortex-Mx port. Note that the 64 bits alignment has a cost both as
+  performance and as space but it is the "standard".
 
 *** 2.0.1 ***
 - FIX: Fixed notification order in input queues (bug 3020708).