diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 982dcae..936940b 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -144,7 +144,9 @@
 build := -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.build obj
 
 # Prefix -I with $(srctree) if it is not an absolute path.
-addtree = $(if $(filter-out -I/%,$(1)),$(patsubst -I%,-I$(srctree)/%,$(1))) $(1)
+# skip if -I has no parameter
+addtree = $(if $(patsubst -I%,%,$(1)), \
+$(if $(filter-out -I/%,$(1)),$(patsubst -I%,-I$(srctree)/%,$(1))) $(1))
 
 # Find all -I options and call addtree
 flags = $(foreach o,$($(1)),$(if $(filter -I%,$(o)),$(call addtree,$(o)),$(o)))