diff --git a/.gitignore b/.gitignore
index 054f2748e..b984b1e5d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -22,3 +22,5 @@ README.pdf
 /downloads
 /tools
 /build
+# local changes only
+make/local.mk
diff --git a/Makefile b/Makefile
index add849a2b..9f3ee3456 100644
--- a/Makefile
+++ b/Makefile
@@ -70,6 +70,8 @@ LINKER_DIR      = $(ROOT)/src/main/target
 ## Build tools, so we all share the same versions
 # import macros common to all supported build systems
 include $(ROOT)/make/system-id.mk
+# developer preferences, edit these at will, they'll be gitignored
+include $(ROOT)/make/local.mk
 
 # configure some directories that are relative to wherever ROOT_DIR is located
 TOOLS_DIR := $(ROOT)/tools
@@ -591,10 +593,10 @@ CCACHE :=
 endif
 
 # Tool names
-CC          := $(CCACHE) $(ARM_SDK_DIR)/bin/arm-none-eabi-gcc
-CPP         := $(CCACHE) $(ARM_SDK_DIR)/bin/arm-none-eabi-g++
-OBJCOPY     := $(ARM_SDK_DIR)/bin/arm-none-eabi-objcopy
-SIZE        := $(ARM_SDK_DIR)/bin/arm-none-eabi-size
+CC          := $(CCACHE) $(ARM_SDK_PREFIX)gcc
+CPP         := $(CCACHE) $(ARM_SDK_PREFIX)g++
+OBJCOPY     := $(ARM_SDK_PREFIX)objcopy
+SIZE        := $(ARM_SDK_PREFIX)size
 
 #
 # Tool options.
diff --git a/make/local.mk b/make/local.mk
new file mode 100644
index 000000000..1b66457a5
--- /dev/null
+++ b/make/local.mk
@@ -0,0 +1,2 @@
+# override the toolchain version, should match the output from of your version of the toolchain: $(arm-none-eabi-gcc -dumpversion)
+#GCC_REQUIRED_VERSION=5.4.1
diff --git a/make/tools.mk b/make/tools.mk
index 77aa88a6c..299086b1b 100644
--- a/make/tools.mk
+++ b/make/tools.mk
@@ -15,6 +15,8 @@
 
 # Set up ARM (STM32) SDK
 ARM_SDK_DIR := $(TOOLS_DIR)/gcc-arm-none-eabi-5_4-2016q2
+# Checked below, Should match the output of $(shell arm-none-eabi-gcc -dumpversion)
+GCC_REQUIRED_VERSION := 5.4.1
 
 .PHONY: arm_sdk_install
 
@@ -271,13 +273,14 @@ zip_clean:
 #
 ##############################
 
+GCC_VERSION=$(shell arm-none-eabi-gcc -dumpversion)
 ifeq ($(shell [ -d "$(ARM_SDK_DIR)" ] && echo "exists"), exists)
   ARM_SDK_PREFIX := $(ARM_SDK_DIR)/bin/arm-none-eabi-
-else
-  ifndef IGNORE_MISSING_TOOLCHAIN
-    ifeq (,$(findstring _install,$(MAKECMDGOALS)))
-      $(error **WARNING** ARM-SDK not in $(ARM_SDK_DIR)  Please run 'make arm_sdk_install')
-    endif
+else ifeq (,$(findstring _install,$(MAKECMDGOALS)))
+  ifeq ($(GCC_VERSION),)
+    $(error **ERROR** arm-none-eabi-gcc not in the PATH. Run 'make arm_sdk_install' to install automatically in the tools folder of this repo)
+  else ifneq ($(GCC_VERSION), $(GCC_REQUIRED_VERSION))
+    $(error **WARNING** your arm-none-eabi-gcc is '$(GCC_VERSION)', but '$(GCC_REQUIRED_VERSION)' is expected. Run 'make arm_sdk_install' to install automatically in the tools folder of this repo)
   endif
   # not installed, hope it's in the path...
   ARM_SDK_PREFIX ?= arm-none-eabi-