diff --git a/make/defs-cpp.mk b/make/defs-cpp.mk
index 7a45d1b1..12a4b61f 100644
--- a/make/defs-cpp.mk
+++ b/make/defs-cpp.mk
@@ -1,6 +1,9 @@
 ifndef JW_BUILD_CPP_DEFS_MK_INCLUDED
 JW_BUILD_CPP_DEFS_MK_INCLUDED := true
 
+# performance optimization for clean targets
+ifeq ($(filter clean distclean,$(MAKECMDGOALS)),)
+
 # -- default choices
 
 #COMPILER_SUITE             ?= clang
@@ -803,4 +806,5 @@ INSTALLED_LIB               += $(INSTALLED_LIB_SO) $(INSTALLED_SHOBJS) \
         $(INSTALLED_LINKS_SO) $(sort $(INSTALLED_LIB_A) $(INSTALLED_ALL_LIBS)) \
         $(INSTALLED_DEF)
 
+endif # ifeq ($(filter clean distclean,$(MAKECMDGOALS)),)
 endif # ifndef JW_BUILD_CPP_DEFS_MK_INCLUDED