diff --git a/src/Wt/WBootstrap5Theme.C b/src/Wt/WBootstrap5Theme.C
index 6ac05fa2..4aa10f5f 100644
--- a/src/Wt/WBootstrap5Theme.C
+++ b/src/Wt/WBootstrap5Theme.C
@@ -6,6 +6,7 @@
 
 #include "Wt/WBootstrap5Theme.h"
 
+#include "Wt/WCompositeWidget.h"
 #include "Wt/WAbstractItemView.h"
 #include "Wt/WAbstractSpinBox.h"
 #include "Wt/WApplication.h"
@@ -245,6 +246,14 @@ void WBootstrap5Theme::apply(WWidget *widget, DomElement& element,
   if (!widget->isThemeStyleEnabled())
     return;
 
+  {
+    auto composite = dynamic_cast<WCompositeWidget *>(widget);
+    if(composite)
+    {
+      widget = composite->implementation();
+    }
+  }
+
   {
     auto popup = dynamic_cast<WPopupWidget *>(widget);
     if (popup) {
diff --git a/src/Wt/WCompositeWidget.h b/src/Wt/WCompositeWidget.h
index bb3367b9..c5e6c9ff 100644
--- a/src/Wt/WCompositeWidget.h
+++ b/src/Wt/WCompositeWidget.h
@@ -8,6 +8,7 @@
 #define WCOMPOSITE_WIDGET_H_
 
 #include <Wt/WWidget.h>
+#include "Wt/WBootstrap5Theme.h"
 
 namespace Wt {
 
@@ -47,6 +48,8 @@ namespace Wt {
  */
 class WT_API WCompositeWidget : public WWidget
 {
+  friend void WBootstrap5Theme::apply(WWidget *widget, DomElement& element,
+                             int elementRole) const;
 public:
   /*! \brief Creates a %WCompositeWidget.
    *