diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index 48ff80958e..e74a095b96 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -307,7 +307,7 @@ config XTENSA_TOOLCHAIN_XCC
 
 config XTENSA_TOOLCHAIN_XCLANG
 	bool "Xtensa Toolchain use CLANG as front end"
-	select ARCH_TOOLCHAIN_GNU
+	select ARCH_TOOLCHAIN_CLANG
 
 config XTENSA_TOOLCHAIN_ESP
 	bool "ESP toolchain for xtensa"
diff --git a/arch/xtensa/src/lx7/Toolchain.defs b/arch/xtensa/src/lx7/Toolchain.defs
index 0f9bef98c5..f8719643fe 100644
--- a/arch/xtensa/src/lx7/Toolchain.defs
+++ b/arch/xtensa/src/lx7/Toolchain.defs
@@ -58,7 +58,11 @@ endif
 ifeq ($(CONFIG_DEBUG_CUSTOMOPT),y)
   ARCHOPTIMIZATION += $(CONFIG_DEBUG_OPTLEVEL)
 else ifeq ($(CONFIG_DEBUG_FULLOPT),y)
-  ARCHOPTIMIZATION += -Os
+  ifeq ($(CONFIG_ARCH_TOOLCHAIN_CLANG),y)
+    ARCHOPTIMIZATION += -Oz
+  else
+    ARCHOPTIMIZATION += -Os
+  endif
 endif
 
 ifneq ($(CONFIG_DEBUG_NOOPT),y)