diff --git a/build-aux/check.mk b/build-aux/check.mk
index 92935d9a3..5bfcc90cf 100644
--- a/build-aux/check.mk
+++ b/build-aux/check.mk
@@ -213,8 +213,8 @@ $(TEST_SUITE_LOG): $(TEST_LOGS)
 	    for f in $(TEST_LOGS);					\
 	    do								\
 	      case $$(sed 1q $$f) in					\
-	        SKIP:*|PASS:*|XFAIL:*);;				\
-	        *) echo; cat $$f;;					\
+		SKIP:*|PASS:*|XFAIL:*);;				\
+		*) echo; cat $$f;;					\
 	      esac;							\
 	    done;							\
 	  } >$(TEST_SUITE_LOG).tmp;					\
diff --git a/maint.mk b/maint.mk
index 31d75f4c0..0c1ad24a6 100644
--- a/maint.mk
+++ b/maint.mk
@@ -537,6 +537,12 @@ changelog-check:
 	  exit 1;							\
 	fi
 
+sc_makefile_TAB_only_indentation:
+	@grep -nE '^	[ ]{8}'						\
+	    $$($(VC_LIST_EXCEPT) | grep -E 'akefile|\.mk$$')		\
+	  && { echo '$(ME): found TAB-8-space indentation' 1>&2;	\
+	       exit 1; } || :
+
 sc_m4_quote_check:
 	@grep -nE '(AC_DEFINE(_UNQUOTED)?|AC_DEFUN)\([^[]'		\
 	    $$($(VC_LIST_EXCEPT) | grep -E '(^configure\.ac|\.m4)$$')	\
@@ -588,7 +594,7 @@ sc_makefile_path_separator_check:
 writable-files:
 	if test -d $(release_archive_dir); then :; else			\
 	  for file in $(distdir).tar.gz					\
-	              $(release_archive_dir)/$(distdir).tar.gz; do	\
+		      $(release_archive_dir)/$(distdir).tar.gz; do	\
 	    test -e $$file || continue;					\
 	    test -w $$file						\
 	      || { echo ERROR: $$file is not writable; fail=1; };	\
@@ -740,8 +746,8 @@ define coreutils-path-check
 	  && ln -sf ../src/true $(bin)/false		\
 	  && PATH=`pwd`/$(bin):$$PATH $(MAKE) -C tests check \
 	  && { test -d gnulib-tests			\
-	         && $(MAKE) -C gnulib-tests check	\
-	         || :; }				\
+		 && $(MAKE) -C gnulib-tests check	\
+		 || :; }				\
 	  && rm -rf $(bin)				\
 	  && fail=0;					\
     else						\
diff --git a/man/Makefile.am b/man/Makefile.am
index 2b2805232..ec5284b24 100644
--- a/man/Makefile.am
+++ b/man/Makefile.am
@@ -156,13 +156,13 @@ mapped_name = `echo $*|sed 's/^install$$/ginstall/; s/^test$$/[/'`
 	  *)							\
 	    rm -f $@						\
 	    && { echo "Updating man page $@";			\
-	         rm -rf $t;					\
-	         mkdir $t;					\
-	         (cd $t && $(LN_S) ../../src/$(mapped_name) $*); \
-	            $(PERL) -- $(srcdir)/help2man		\
-	             --source='$(PACKAGE_STRING)'		\
-	             --include=$(srcdir)/$*.x			\
-	             --output=$t/$@ $t/$*;			\
+		 rm -rf $t;					\
+		 mkdir $t;					\
+		 (cd $t && $(LN_S) ../../src/$(mapped_name) $*); \
+		    $(PERL) -- $(srcdir)/help2man		\
+		     --source='$(PACKAGE_STRING)'		\
+		     --include=$(srcdir)/$*.x			\
+		     --output=$t/$@ $t/$*;			\
 	       }						\
 	    && sed 's|$*\.td/||g' $t/$@ > $@			\
 	    && rm -rf $t ;;					\