diff --git a/web.config b/web.config
index bb423f8e..661d7fb4 100644
--- a/web.config
+++ b/web.config
@@ -23,6 +23,12 @@
             </conditions>
             <action type="Redirect" url="https://{SERVER_NAME}/{R:1}" redirectType="Permanent" />
         </rule>
+        
+        <!-- Allow Let's Encrypt ACME challenge requests -->
+	   <rule name="LetsEncryptAcmeChallenge" stopProcessing="true">
+               <match url="^\.well-known.*$" />
+               <action type="None" />
+        </rule>
                   
         <!-- Do not interfere with requests for node-inspector debugging -->
         <rule name="NodeInspector" patternSyntax="ECMAScript" stopProcessing="true">
@@ -66,4 +72,4 @@
     -->
     <!--<iisnode watchedFiles="web.config;*.js"/>-->
   </system.webServer>
-</configuration>
\ No newline at end of file
+</configuration>