diff --git a/aclocal.m4 b/aclocal.m4
index c1bdcbc93c..faf6beb7d4 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -2,7 +2,7 @@
 
 AC_DEFUN([_COLORIZE_RESULT_PREPARE], [
     msg_checking= msg_result_yes= msg_result_no= msg_result_other= msg_reset=
-    AS_IF([test -t], [
+    AS_IF([test -t 1], [
 	msg_begin="`tput smso 2>/dev/null`"
     	AS_CASE(["$msg_begin"], ['@<:@'*m],
 	    [msg_begin="`echo "$msg_begin" | sed ['s/[0-9]*m$//']`"
diff --git a/tool/ifchange b/tool/ifchange
index 6a1923c167..837dd4dd16 100755
--- a/tool/ifchange
+++ b/tool/ifchange
@@ -38,7 +38,7 @@ if [ "$temp" = - ]; then
 fi
 
 msg_begin= msg_unchanged= msg_updated= msg_reset=
-if [ -t ]; then
+if [ -t 1 ]; then
     msg_begin="`tput smso 2>/dev/null`"
     case "$msg_begin" in
 	""*m)