diff --git a/bare-arm/Makefile b/bare-arm/Makefile
index a57ccfd196..6ee8552628 100644
--- a/bare-arm/Makefile
+++ b/bare-arm/Makefile
@@ -13,7 +13,7 @@ INC += -I..
 INC += -I$(BUILD)
 
 CFLAGS_CORTEX_M4 = -mthumb -mtune=cortex-m4 -mabi=aapcs-linux -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard -fsingle-precision-constant -Wdouble-promotion
-CFLAGS = $(INC) -Wall -Werror -ansi -std=gnu99 -nostdlib $(CFLAGS_CORTEX_M4) $(COPT)
+CFLAGS = $(INC) -Wall -Werror -std=gnu99 -nostdlib $(CFLAGS_CORTEX_M4) $(COPT)
 
 #Debugging/Optimization
 ifeq ($(DEBUG), 1)
diff --git a/cc3200/Makefile b/cc3200/Makefile
index 4db3b9e8d3..663496435b 100644
--- a/cc3200/Makefile
+++ b/cc3200/Makefile
@@ -20,7 +20,7 @@ include ../py/mkenv.mk
 CROSS_COMPILE ?= arm-none-eabi-
 
 CFLAGS_CORTEX_M4 = -mthumb -mtune=cortex-m4 -march=armv7e-m -mabi=aapcs -mcpu=cortex-m4 -msoft-float -mfloat-abi=soft -fsingle-precision-constant -Wdouble-promotion
-CFLAGS = -Wall -Wpointer-arith -Werror -ansi -std=gnu99 -nostdlib $(CFLAGS_CORTEX_M4) -Os
+CFLAGS = -Wall -Wpointer-arith -Werror -std=gnu99 -nostdlib $(CFLAGS_CORTEX_M4) -Os
 CFLAGS += -g -ffunction-sections -fdata-sections -fno-common -fsigned-char -mno-unaligned-access
 CFLAGS += -Iboards/$(BOARD)
 CFLAGS += $(CFLAGS_MOD)
diff --git a/esp8266/Makefile b/esp8266/Makefile
index 5e61fc16d8..4710f4cdc2 100644
--- a/esp8266/Makefile
+++ b/esp8266/Makefile
@@ -41,7 +41,7 @@ CFLAGS_XTENSA = -fsingle-precision-constant -Wdouble-promotion \
 	-Wl,-EL -mlongcalls -mtext-section-literals -mforce-l32 \
 	-DLWIP_OPEN_SRC
 
-CFLAGS = $(INC) -Wall -Wpointer-arith -Werror -ansi -std=gnu99 -nostdlib -DUART_OS=$(UART_OS) \
+CFLAGS = $(INC) -Wall -Wpointer-arith -Werror -std=gnu99 -nostdlib -DUART_OS=$(UART_OS) \
 	$(CFLAGS_XTENSA) $(CFLAGS_MOD) $(COPT) $(CFLAGS_EXTRA)
 
 LDSCRIPT = esp8266.ld
diff --git a/examples/embedding/Makefile.upylib b/examples/embedding/Makefile.upylib
index d8dbade3fe..8b506e95e7 100644
--- a/examples/embedding/Makefile.upylib
+++ b/examples/embedding/Makefile.upylib
@@ -20,7 +20,7 @@ INC += -I$(BUILD)
 # compiler settings
 CWARN = -Wall -Werror
 CWARN += -Wpointer-arith -Wuninitialized
-CFLAGS = $(INC) $(CWARN) -ansi -std=gnu99 -DUNIX $(CFLAGS_MOD) $(COPT) $(CFLAGS_EXTRA)
+CFLAGS = $(INC) $(CWARN) -std=gnu99 -DUNIX $(CFLAGS_MOD) $(COPT) $(CFLAGS_EXTRA)
 
 # Debugging/Optimization
 ifdef DEBUG
diff --git a/minimal/Makefile b/minimal/Makefile
index 4117517352..42c2d53127 100644
--- a/minimal/Makefile
+++ b/minimal/Makefile
@@ -22,9 +22,9 @@ ifeq ($(CROSS), 1)
 DFU = ../tools/dfu.py
 PYDFU = ../tools/pydfu.py
 CFLAGS_CORTEX_M4 = -mthumb -mtune=cortex-m4 -mabi=aapcs-linux -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard -fsingle-precision-constant -Wdouble-promotion
-CFLAGS = $(INC) -Wall -Werror -ansi -std=gnu99 -nostdlib $(CFLAGS_CORTEX_M4) $(COPT)
+CFLAGS = $(INC) -Wall -Werror -std=gnu99 -nostdlib $(CFLAGS_CORTEX_M4) $(COPT)
 else
-CFLAGS = -m32 $(INC) -Wall -Werror -ansi -std=gnu99 $(COPT)
+CFLAGS = -m32 $(INC) -Wall -Werror -std=gnu99 $(COPT)
 endif
 
 #Debugging/Optimization
diff --git a/mpy-cross/Makefile b/mpy-cross/Makefile
index 3f99566209..3d5e5da2f9 100644
--- a/mpy-cross/Makefile
+++ b/mpy-cross/Makefile
@@ -19,7 +19,7 @@ INC += -I$(BUILD)
 # compiler settings
 CWARN = -Wall -Werror
 CWARN += -Wpointer-arith -Wuninitialized
-CFLAGS = $(INC) $(CWARN) -ansi -std=gnu99 $(CFLAGS_MOD) $(COPT) $(CFLAGS_EXTRA)
+CFLAGS = $(INC) $(CWARN) -std=gnu99 $(CFLAGS_MOD) $(COPT) $(CFLAGS_EXTRA)
 CFLAGS += -fdata-sections -ffunction-sections -fno-asynchronous-unwind-tables
 
 # Debugging/Optimization
diff --git a/pic16bit/Makefile b/pic16bit/Makefile
index cfe8af86ec..add9a8495c 100644
--- a/pic16bit/Makefile
+++ b/pic16bit/Makefile
@@ -21,7 +21,7 @@ INC += -I$(XC16)/include
 INC += -I$(XC16)/support/$(PARTFAMILY)/h
 
 CFLAGS_PIC16BIT = -mcpu=$(PART) -mlarge-code
-CFLAGS = $(INC) -Wall -Werror -ansi -std=gnu99 -nostdlib $(CFLAGS_PIC16BIT) $(COPT)
+CFLAGS = $(INC) -Wall -Werror -std=gnu99 -nostdlib $(CFLAGS_PIC16BIT) $(COPT)
 
 #Debugging/Optimization
 ifeq ($(DEBUG), 1)
diff --git a/qemu-arm/Makefile b/qemu-arm/Makefile
index 61fc243642..e8f5b359ef 100644
--- a/qemu-arm/Makefile
+++ b/qemu-arm/Makefile
@@ -15,7 +15,7 @@ INC += -I$(BUILD)
 INC += -I../tools/tinytest/
 
 CFLAGS_CORTEX_M3 = -mthumb -mcpu=cortex-m3 -mfloat-abi=soft
-CFLAGS = $(INC) -Wall -Wpointer-arith -Werror -ansi -std=gnu99 $(CFLAGS_CORTEX_M3) $(COPT) \
+CFLAGS = $(INC) -Wall -Wpointer-arith -Werror -std=gnu99 $(CFLAGS_CORTEX_M3) $(COPT) \
 	 -ffunction-sections -fdata-sections
 
 #Debugging/Optimization
diff --git a/stmhal/Makefile b/stmhal/Makefile
index 76579d1305..3eef6ffb23 100644
--- a/stmhal/Makefile
+++ b/stmhal/Makefile
@@ -56,7 +56,7 @@ CFLAGS_MCU_f4 = $(CFLAGS_CORTEX_M) -mtune=cortex-m4 -mcpu=cortex-m4 -DMCU_SERIES
 CFLAGS_MCU_f7 = $(CFLAGS_CORTEX_M) -mtune=cortex-m7 -mcpu=cortex-m7 -DMCU_SERIES_F7
 CFLAGS_MCU_l4 = $(CFLAGS_CORTEX_M) -mtune=cortex-m4 -mcpu=cortex-m4 -DMCU_SERIES_L4
 
-CFLAGS = $(INC) -Wall -Wpointer-arith -Werror -ansi -std=gnu99 -nostdlib $(CFLAGS_MOD)
+CFLAGS = $(INC) -Wall -Wpointer-arith -Werror -std=gnu99 -nostdlib $(CFLAGS_MOD)
 CFLAGS += -D$(CMSIS_MCU)
 CFLAGS += $(CFLAGS_MCU_$(MCU_SERIES))
 CFLAGS += $(COPT)
diff --git a/teensy/Makefile b/teensy/Makefile
index 82e04a1ae3..e613b8f271 100644
--- a/teensy/Makefile
+++ b/teensy/Makefile
@@ -36,7 +36,7 @@ INC += -I../lib/mp-readline
 INC += -I$(BUILD)
 INC += -Icore
 
-CFLAGS = $(INC) -Wall -Wpointer-arith -ansi -std=gnu99 -nostdlib $(CFLAGS_CORTEX_M4)
+CFLAGS = $(INC) -Wall -Wpointer-arith -std=gnu99 -nostdlib $(CFLAGS_CORTEX_M4)
 LDFLAGS = -nostdlib -T mk20dx256.ld -msoft-float -mfloat-abi=soft
 
 ifeq ($(USE_ARDUINO_TOOLCHAIN),1)
diff --git a/unix/Makefile b/unix/Makefile
index 83bd3f984c..f28a4bcae9 100644
--- a/unix/Makefile
+++ b/unix/Makefile
@@ -23,7 +23,7 @@ INC += -I$(BUILD)
 # compiler settings
 CWARN = -Wall -Werror
 CWARN += -Wpointer-arith -Wuninitialized
-CFLAGS = $(INC) $(CWARN) -ansi -std=gnu99 -DUNIX $(CFLAGS_MOD) $(COPT) $(CFLAGS_EXTRA)
+CFLAGS = $(INC) $(CWARN) -std=gnu99 -DUNIX $(CFLAGS_MOD) $(COPT) $(CFLAGS_EXTRA)
 
 # Debugging/Optimization
 ifdef DEBUG
diff --git a/windows/Makefile b/windows/Makefile
index 68de66a071..72c97381bd 100644
--- a/windows/Makefile
+++ b/windows/Makefile
@@ -15,7 +15,7 @@ INC += -I..
 INC += -I$(BUILD)
 
 # compiler settings
-CFLAGS = $(INC) -Wall -Wpointer-arith -Werror -ansi -std=gnu99 -DUNIX -D__USE_MINGW_ANSI_STDIO=1 $(CFLAGS_MOD) $(COPT)
+CFLAGS = $(INC) -Wall -Wpointer-arith -Werror -std=gnu99 -DUNIX -D__USE_MINGW_ANSI_STDIO=1 $(CFLAGS_MOD) $(COPT)
 LDFLAGS = $(LDFLAGS_MOD) -lm
 
 # Debugging/Optimization