diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 24a33c01bbf7..9c689d011bce 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -234,6 +234,9 @@ objtool_dep = $(objtool_obj)					\
 ifdef CONFIG_TRIM_UNUSED_KSYMS
 cmd_gen_ksymdeps = \
 	$(CONFIG_SHELL) $(srctree)/scripts/gen_ksymdeps.sh $@ >> $(dot-target).cmd
+
+# List module undefined symbols
+undefined_syms = $(NM) $< | $(AWK) '$$1 == "U" { printf("%s%s", x++ ? " " : "", $$2) }';
 endif
 
 define rule_cc_o_c
@@ -253,13 +256,6 @@ define rule_as_o_S
 	$(call cmd,modversions_S)
 endef
 
-# List module undefined symbols (or empty line if not enabled)
-ifdef CONFIG_TRIM_UNUSED_KSYMS
-cmd_undef_syms = $(NM) $< | sed -n 's/^  *U //p' | xargs echo
-else
-cmd_undef_syms = echo
-endif
-
 # Built-in and composite module parts
 $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
 	$(call cmd,force_checksrc)
@@ -267,7 +263,7 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
 
 cmd_mod = { \
 	echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \
-	$(cmd_undef_syms); \
+	$(undefined_syms) echo; \
 	} > $@
 
 $(obj)/%.mod: $(obj)/%.o FORCE