diff --git a/host/xtest/Makefile b/host/xtest/Makefile
index 8564ddd..7b3de36 100644
--- a/host/xtest/Makefile
+++ b/host/xtest/Makefile
@@ -24,6 +24,15 @@
 OBJDUMP		?= $(CROSS_COMPILE)objdump
 READELF		?= $(CROSS_COMPILE)readelf
 
+# Macros to detect the targeted architecture (e.g., arm-linux-gnueabihf or
+# aarch64-linux-gnu) and the corresponding bit size (32 or 64).
+define cc-arch
+$(shell $(1) -v 2>&1 | grep Target | sed 's/Target: \([^-]*\).*/\1/')
+endef
+define cc-bits
+$(if $(filter arm, $(1)),32,$(if $(filter aarch64, $(1)),64,unknown-arch))
+endef
+
 # OpenSSL is used by GP tests series 8500 and Mbed TLS test 8103
 ifneq ($(CFG_GP_PACKAGE_PATH)$(filter y,$(CFG_TA_MBEDTLS)),)
 CFLAGS += -DOPENSSL_FOUND=1
@@ -32,7 +41,7 @@
 CFLAGS += -I$(OPTEE_OPENSSL_EXPORT)
 else #OPTEE_OPENSSL_EXPORT
 CFLAGS += -I../openssl/include
-ifeq ($(COMPILE_NS_USER),32)
+ifeq ($(call cc-bits, $(call cc-arch, $(CC))),32)
 LDFLAGS += ../openssl/lib/arm/libcrypto.a -ldl
 else
 LDFLAGS += ../openssl/lib/aarch64/libcrypto.a -ldl
@@ -132,13 +141,6 @@
 CFLAGS += -I../../ta/GP_TTA_testingClientAPI
 
 
-# by default, the client application is compiled as the kernel of optee-os
-ifeq ($(CFG_ARM32_core),y)
-COMPILE_NS_USER ?= 32
-else
-COMPILE_NS_USER ?= 64
-endif
-
 endif
 
 TA_DIR ?= /lib/optee_armtz