diff --git a/docs/configuration/configuration.md b/docs/configuration/configuration.md
index 3856a138ee..776529ae11 100644
--- a/docs/configuration/configuration.md
+++ b/docs/configuration/configuration.md
@@ -135,6 +135,14 @@ If this option is active /login will lead directly to the configured omniauth pr
 Note that this does not stop a user from manually navigating to any other
 omniauth provider if additional ones are configured.
 
+
+### Gravatar images
+
+OpenProject uses gravatar images with a `404` fallback by default to render an internal, initials-based avatar.
+You can override this behavior by setting `gravatar_fallback_image` to a different value.
+
+For supported values, please see https://en.gravatar.com/site/implement/images/
+
 ### attachments storage
 
 *default: file*
diff --git a/lib/open_project/configuration.rb b/lib/open_project/configuration.rb
index 4374e54fdd..8fb8e04af8 100644
--- a/lib/open_project/configuration.rb
+++ b/lib/open_project/configuration.rb
@@ -129,6 +129,9 @@ module OpenProject
       # Allow in-context translations to be loaded with CSP
       'crowdin_in_context_translations' => true,
 
+      # Default gravatar image, set to something other than 404
+      # to ensure a default is returned
+      'gravatar_fallback_image' => '404',
 
       'registration_footer' => {},
 
diff --git a/modules/avatars/lib/open_project/avatars/patches/avatar_helper_patch.rb b/modules/avatars/lib/open_project/avatars/patches/avatar_helper_patch.rb
index 608e987282..55090266c4 100644
--- a/modules/avatars/lib/open_project/avatars/patches/avatar_helper_patch.rb
+++ b/modules/avatars/lib/open_project/avatars/patches/avatar_helper_patch.rb
@@ -119,7 +119,7 @@ AvatarHelper.class_eval do
 
     def default_gravatar_options
       options = { secure: Setting.protocol == 'https' }
-      options[:default] = '404'
+      options[:default] = OpenProject::Configuration.gravatar_fallback_image
 
       options
     end