diff --git a/arch/arm/src/arm/Toolchain.defs b/arch/arm/src/arm/Toolchain.defs
index c4ee7567685..b5276990b6f 100644
--- a/arch/arm/src/arm/Toolchain.defs
+++ b/arch/arm/src/arm/Toolchain.defs
@@ -87,7 +87,7 @@ endif
 
 CC = $(CROSSDEV)gcc
 CXX = $(CROSSDEV)g++
-CPP = $(CROSSDEV)gcc -E
+CPP = $(CROSSDEV)gcc -E -P -x c
 LD = $(CROSSDEV)ld
 STRIP = $(CROSSDEV)strip --strip-unneeded
 AR = $(CROSSDEV)ar rcs