diff --git a/lib/stm32/f7/Makefile b/lib/stm32/f7/Makefile
index db0d8886..3c894045 100644
--- a/lib/stm32/f7/Makefile
+++ b/lib/stm32/f7/Makefile
@@ -56,7 +56,7 @@ Your toolchain doesn't support -mcpu=cortex-m7.
 Please use gcc-arm-embedded 4.8 2014q3 or newer. Skipping this sub-library.
 endef
 
-ifneq ($($(CC) --help=target | grep -q '\<cortex-m7\>'; echo $$?),0)
+ifneq ($(shell $(CC) --help=target | grep -q '\<cortex-m7\>'; echo $$?),0)
   $(warning $(MISSING_CPU))
 
 all clean: