diff --git a/arch/arm/src/common/Toolchain.defs b/arch/arm/src/common/Toolchain.defs
index 35d90f2c732..2f5e7fddbd5 100644
--- a/arch/arm/src/common/Toolchain.defs
+++ b/arch/arm/src/common/Toolchain.defs
@@ -35,6 +35,8 @@ ifeq ($(CONFIG_DEBUG_CUSTOMOPT),y)
 else ifeq ($(CONFIG_DEBUG_FULLOPT),y)
   ifeq ($(CONFIG_ARCH_TOOLCHAIN_CLANG),y)
     ARCHOPTIMIZATION += -Oz
+  else ifeq ($(CONFIG_ARM_TOOLCHAIN_GHS),y)
+    ARCHOPTIMIZATION += -Osize
   else
     ARCHOPTIMIZATION += -Os
   endif