diff --git a/NEWS b/NEWS
index baa80932..63af1b44 100644
--- a/NEWS
+++ b/NEWS
@@ -6,6 +6,8 @@ shiny-server 1.5.20
   then deploy the generated index.html, index_files directory, and the source
   index.qmd together to be served by Shiny Server.
 
+* Fix bug where Shiny for Python apps did not work for `app_dir` directives.
+
 shiny-server 1.5.19
 --------------------------------------------------------------------------------
 
diff --git a/lib/router/router.js b/lib/router/router.js
index 9fa01af8..aea577ac 100644
--- a/lib/router/router.js
+++ b/lib/router/router.js
@@ -247,13 +247,15 @@ function SingleAppRouter(appdir, runas, prefix, logDir, settings) {
       var app = _.find(files, function(entry) {
         return /^server\.r$/i.test(entry);
       });
-
       var singleApp = _.find(files, function(entry) {
         return /^app\.r$/i.test(entry);
       });
       var rmd = _.find(files, function(entry) {
         return /\.[rq]md$/i.test(entry);
       });
+      var pyApp = _.find(files, function(entry) {
+        return /^app\.py$/.test(entry);
+      });
       var indexRmd = _.find(files, function(entry) {
         if (/^index\.[rq]md$/i.test(entry)){
           return entry;
@@ -296,6 +298,8 @@ function SingleAppRouter(appdir, runas, prefix, logDir, settings) {
           .done();
           return true;
         }
+      } else if (pyApp) {
+        appSpec.settings.mode = "shiny-python";
       } else{
         // No app found.
       }