diff --git a/app/models/protocol.rb b/app/models/protocol.rb
index 5bb38bb76..dd0237e9f 100644
--- a/app/models/protocol.rb
+++ b/app/models/protocol.rb
@@ -364,8 +364,8 @@ class Protocol < ApplicationRecord
     steps.where(completed: true)
   end
 
-  def first_step
-    steps.find_by(position: 0)
+  def first_step_id
+    steps.find_by(position: 0)&.id
   end
 
   def space_taken
diff --git a/app/views/my_modules/_open_mobile_app.html.erb b/app/views/my_modules/_open_mobile_app.html.erb
index 6524984f0..823cb1f16 100644
--- a/app/views/my_modules/_open_mobile_app.html.erb
+++ b/app/views/my_modules/_open_mobile_app.html.erb
@@ -6,7 +6,7 @@
   <div class="open-mobile-app-buttons">
     <a type="button"
        class="btn btn-dark-background btn-large"
-       href="<%= pwa_mobile_app_url(@current_team.id, @project.id, @experiment.id, @my_module.id, @protocol.id, @protocol.first_step.id, request.host) %>">
+       href="<%= pwa_mobile_app_url(@current_team.id, @project.id, @experiment.id, @my_module.id, @protocol.id, @protocol.first_step_id, request.host) %>">
       <i class="fas fa-mobile-alt"></i>
       <%= t('my_modules.open_mobile_app.open_mobile_app') %>
     </a>