diff --git a/configure b/configure
index 14be411..41950d6 100755
--- a/configure
+++ b/configure
@@ -1,8 +1,9 @@
 #!/bin/sh
 
-[ -z $CC ] && CC=gcc
-[ -z $CFLAGS ] && CFLAGS="-I/usr/X11R6/include"
-[ -z $LDFLAGS ] && LDFLAGS="-L/usr/X11R6/lib"
+
+test x"$CC" != "x" || CC=gcc
+test x"$CFLAGS" != "x" || CFLAGS="-I/usr/X11R6/include"
+test x"$LDFLAGS" != "x" || LDFLAGS="-L/usr/X11R6/lib"
 
 CHECK_XRENDER=0
 CHECK_XCURSOR=0
@@ -37,11 +38,11 @@ check_docs() {
 check_tools() {
 
     msg_chkfor "gcc"
-    if which $CC 1> /dev/null 2>&3
+    if which "$CC" 1> /dev/null 2>&3
     then
         echo "ok."
         echo "---------------------------------" 1>&3
-        $CC -v 1>&3 2>&3
+        "$CC" -v 1>&3 2>&3
         echo "---------------------------------" 1>&3
     else
         echo "no."