diff --git a/demos/constraint-editor/constraint-editor-window.ui b/demos/constraint-editor/constraint-editor-window.ui
index aa809e393a..fab5b8d1d4 100644
--- a/demos/constraint-editor/constraint-editor-window.ui
+++ b/demos/constraint-editor/constraint-editor-window.ui
@@ -1,9 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
   <template class="ConstraintEditorWindow" parent="GtkApplicationWindow">
-    <style>
-      <class name="devel"/>
-    </style>
     <property name="title" translatable="yes">GTK Constraint Editor</property>
     <property name="default-width">1024</property>
     <property name="default-height">768</property>
diff --git a/demos/gtk-demo/main.ui b/demos/gtk-demo/main.ui
index 484cc63b05..d4df910ef3 100644
--- a/demos/gtk-demo/main.ui
+++ b/demos/gtk-demo/main.ui
@@ -17,9 +17,6 @@
     </section>
   </menu>
   <object class="GtkApplicationWindow" id="window">
-    <style>
-      <class name="devel"/>
-    </style>
     <property name="default-width">800</property>
     <property name="default-height">600</property>
     <child type="titlebar">
diff --git a/demos/icon-browser/window.ui b/demos/icon-browser/window.ui
index 7dc204e41f..59685dbb57 100644
--- a/demos/icon-browser/window.ui
+++ b/demos/icon-browser/window.ui
@@ -13,9 +13,6 @@
     </section>
   </menu>
   <template class="IconBrowserWindow" parent="GtkApplicationWindow">
-    <style>
-      <class name="devel"/>
-    </style>
     <property name="title" translatable="yes">Icon Browser</property>
     <property name="default-width">1024</property>
     <property name="default-height">768</property>
diff --git a/demos/node-editor/help-window.ui b/demos/node-editor/help-window.ui
index a5387393db..7feffb7c18 100644
--- a/demos/node-editor/help-window.ui
+++ b/demos/node-editor/help-window.ui
@@ -1,9 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
   <object class="GtkWindow" id="window">
-    <style>
-      <class name="devel"/>
-    </style>
     <property name="title" translatable="yes">Help</property>
     <property name="default-width">720</property>
     <property name="default-height">520</property>
diff --git a/demos/node-editor/node-editor-window.ui b/demos/node-editor/node-editor-window.ui
index b7e94f9e8f..20d36f6f28 100644
--- a/demos/node-editor/node-editor-window.ui
+++ b/demos/node-editor/node-editor-window.ui
@@ -94,9 +94,6 @@
   </object>
 
   <template class="NodeEditorWindow" parent="GtkApplicationWindow">
-    <style>
-      <class name="devel"/>
-    </style>
     <property name="title" translatable="yes">GTK Node Editor</property>
     <property name="default-width">1024</property>
     <property name="default-height">768</property>
diff --git a/demos/print-editor/print-editor.c b/demos/print-editor/print-editor.c
index a0c8da320d..838c421b29 100644
--- a/demos/print-editor/print-editor.c
+++ b/demos/print-editor/print-editor.c
@@ -812,8 +812,6 @@ activate (GApplication *app)
   gtk_application_window_set_show_menubar (GTK_APPLICATION_WINDOW (main_window), TRUE);
   update_title (GTK_WINDOW (main_window));
 
-  gtk_widget_add_css_class (main_window, "devel");
-
   box = gtk_box_new (GTK_ORIENTATION_VERTICAL, 0);
   gtk_window_set_child (GTK_WINDOW (main_window), box);
 
diff --git a/demos/widget-factory/widget-factory.ui b/demos/widget-factory/widget-factory.ui
index 8f78b65a5f..ba2378ba34 100644
--- a/demos/widget-factory/widget-factory.ui
+++ b/demos/widget-factory/widget-factory.ui
@@ -433,9 +433,6 @@ Suspendisse feugiat quam quis dolor accumsan cursus.</property>
     </columns>
   </object>
   <object class="GtkApplicationWindow" id="window">
-    <style>
-      <class name="devel"/>
-    </style>
     <property name="title">GTK Widget Factory</property>
     <child type="titlebar">
       <object class="GtkHeaderBar" id="headerbar1">
diff --git a/gtk/inspector/window.ui b/gtk/inspector/window.ui
index 3940f79ee5..c76af022c6 100644
--- a/gtk/inspector/window.ui
+++ b/gtk/inspector/window.ui
@@ -10,9 +10,6 @@
   <template class="GtkInspectorWindow" parent="GtkWindow">
     <property name="default-height">500</property>
     <property name="default-width">800</property>
-    <style>
-      <class name="devel"/>
-    </style>
     <child type="titlebar">
       <object class="GtkHeaderBar">
         <child>
diff --git a/testsuite/gtk/focus-chain/widget-factory.ui b/testsuite/gtk/focus-chain/widget-factory.ui
index b5e1898497..654671b4fd 100644
--- a/testsuite/gtk/focus-chain/widget-factory.ui
+++ b/testsuite/gtk/focus-chain/widget-factory.ui
@@ -433,9 +433,6 @@ Suspendisse feugiat quam quis dolor accumsan cursus.</property>
     </columns>
   </object>
   <object class="GtkApplicationWindow" id="window">
-    <style>
-      <class name="devel"/>
-    </style>
     <property name="title">GTK Widget Factory</property>
     <child type="titlebar">
       <object class="GtkHeaderBar" id="headerbar1">
diff --git a/testsuite/gtk/focus-chain/widget-factory2.ui b/testsuite/gtk/focus-chain/widget-factory2.ui
index df73b1f642..5dd9037329 100644
--- a/testsuite/gtk/focus-chain/widget-factory2.ui
+++ b/testsuite/gtk/focus-chain/widget-factory2.ui
@@ -433,9 +433,6 @@ Suspendisse feugiat quam quis dolor accumsan cursus.</property>
     </columns>
   </object>
   <object class="GtkApplicationWindow" id="window">
-    <style>
-      <class name="devel"/>
-    </style>
     <property name="title">GTK Widget Factory</property>
     <child type="titlebar">
       <object class="GtkHeaderBar" id="headerbar1">
diff --git a/testsuite/gtk/focus-chain/widget-factory3.ui b/testsuite/gtk/focus-chain/widget-factory3.ui
index 8b0a159418..b6d52bea51 100644
--- a/testsuite/gtk/focus-chain/widget-factory3.ui
+++ b/testsuite/gtk/focus-chain/widget-factory3.ui
@@ -433,9 +433,6 @@ Suspendisse feugiat quam quis dolor accumsan cursus.</property>
     </columns>
   </object>
   <object class="GtkApplicationWindow" id="window">
-    <style>
-      <class name="devel"/>
-    </style>
     <property name="title">GTK Widget Factory</property>
     <child type="titlebar">
       <object class="GtkHeaderBar" id="headerbar1">