diff --git a/server/mail/postfix.xml b/server/mail/postfix.xml
index 51e6d76c52..2e263fa897 100644
--- a/server/mail/postfix.xml
+++ b/server/mail/postfix.xml
@@ -139,6 +139,13 @@ chown -v postfix:postfix /var/mail</userinput></screen>
 
 <screen><userinput>sed -i 's/.\x08//g' README_FILES/*</userinput></screen>
 
+      <para>
+        If you are running a linux-4.x kernel, apply the following sed to
+        allow the <command>makedefs</command> script to recognize it:
+      </para>
+
+<screen><userinput>sed -i 's/Linux.3\*/Linux.[34]\*/' makedefs</userinput></screen>
+
       <para>
         The <application>Postfix</application> source tree does not contain a
         <filename>configure</filename> script, rather the makefile in the