diff --git a/docs/nmap-install.xml b/docs/nmap-install.xml
index 7be9de4af..bb8213435 100644
--- a/docs/nmap-install.xml
+++ b/docs/nmap-install.xml
@@ -1333,6 +1333,14 @@ $ <userinput>gcc -print-prog-name=as</userinput>
 /usr/bin/as
 </screen>
 
+<para>
+If you see the output <computeroutput>/usr/bin/as</computeroutput>, then
+you must disable the system <filename>as</filename> with a command like
+<command>mv /usr/bin/as /usr/bin/as.backup</command>. If you see the
+output <computeroutput>as</computeroutput>, then no other changes should
+be required.
+</para>
+
 <para>
 Now follow the instructions in <xref linkend="inst-source"/>.
 </para>