diff --git a/m4/zlib.m4 b/m4/zlib.m4
index 8407838a..d5fbc675 100644
--- a/m4/zlib.m4
+++ b/m4/zlib.m4
@@ -5,14 +5,14 @@ AC_DEFUN(tinc_ZLIB,
   tinc_ac_save_CPPFLAGS="$CPPFLAGS"
 
   AC_ARG_WITH(zlib-include,
-    [  --with-zlib-include=DIR  zlib headers directory],
+    [  --with-zlib-include=DIR zlib headers directory],
     [zlib_include="$withval"
      CFLAGS="$CFLAGS -I$withval"
      CPPFLAGS="$CPPFLAGS -I$withval"]
   )
 
   AC_ARG_WITH(zlib-lib,
-    [  --with-zlib-lib=DIR  zlib library directory],
+    [  --with-zlib-lib=DIR     zlib library directory],
     [zlib_lib="$withval"
      LIBS="$LIBS -L$withval"]
   )