diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index d1d51e38b55d..e67f066c0cea 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -213,9 +213,9 @@ endif
 # $(objtree)/$(obj) for including generated headers from checkin source files
 ifeq ($(KBUILD_EXTMOD),)
 ifdef building_out_of_srctree
-_c_flags   += -I $(srctree)/$(src) -I $(objtree)/$(obj)
-_a_flags   += -I $(srctree)/$(src) -I $(objtree)/$(obj)
-_cpp_flags += -I $(srctree)/$(src) -I $(objtree)/$(obj)
+_c_flags   += $(addprefix -I $(srctree)/,$(src)) $(addprefix -I $(objtree)/,$(obj))
+_a_flags   += $(addprefix -I $(srctree)/,$(src)) $(addprefix -I $(objtree)/,$(obj))
+_cpp_flags += $(addprefix -I $(srctree)/,$(src)) $(addprefix -I $(objtree)/,$(obj))
 endif
 endif