diff --git a/.travis.yml b/.travis.yml
index 412ed1c..57b7204 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,7 +8,7 @@ jobs:
   include:
 
     - name: make (gcc-arm-none-eabi-7)
-      script: make
+      script: make -e VARIANT=VARIANT_ADC
       language: c
       addons:
         apt:
@@ -26,7 +26,7 @@ jobs:
       before_script: arm-none-eabi-gcc --version
 
     - name: make (gcc-arm-none-eabi-5)
-      script: make -e VARIANT_ADC
+      script: make -e VARIANT=VARIANT_ADC
       language: c
       addons:
         apt:
diff --git a/Makefile b/Makefile
index 897c341..10f5b6b 100644
--- a/Makefile
+++ b/Makefile
@@ -55,8 +55,8 @@ startup_stm32f103xe.s
 #######################################
 # binaries
 #######################################
-PREFIX = arm-none-eabi-
-#PREFIX = gcc-arm-none-eabi-7/bin/arm-none-eabi-
+#PREFIX = arm-none-eabi-
+PREFIX = gcc-arm-none-eabi-7/bin/arm-none-eabi-
 CC = $(PREFIX)gcc
 AS = $(PREFIX)gcc -x assembler-with-cpp
 CP = $(PREFIX)objcopy
@@ -111,11 +111,16 @@ ifeq ($(DEBUG), 1)
 CFLAGS += -g -gdwarf-2
 endif
 
+# Choose variant from env var
+# make -e VARIANT=VARIANT_ADC
+
+ifneq ($(VARIANT), )
+CFLAGS += -D $(VARIANT)
+endif
 
 # Generate dependency information
 CFLAGS += -MMD -MP -MF"$(@:%.o=%.d)" -MT"$(@:%.o=%.d)"
 
-
 #######################################
 # LDFLAGS
 #######################################