3 files changed, 15 insertions, 0 deletions
diff --git a/include/pugl/detail/mac.h b/include/pugl/detail/mac.h
index 7b64cfe..55f24ca 100644
--- a/include/pugl/detail/mac.h
+++ b/include/pugl/detail/mac.h
@@ -20,6 +20,9 @@
    @brief Shared definitions for MacOS implementation.
 */
 
+#ifndef PUGL_DETAIL_MAC_H
+#define PUGL_DETAIL_MAC_H
+
 #include "pugl/pugl.h"
 
 #import <Cocoa/Cocoa.h>
@@ -53,3 +56,5 @@ struct PuglInternalsImpl {
 	uint32_t         mods;
 	bool             mouseTracked;
 };
+
+#endif // PUGL_DETAIL_MAC_H
diff --git a/include/pugl/detail/win.h b/include/pugl/detail/win.h
index b0d92e0..0ead1fa 100644
--- a/include/pugl/detail/win.h
+++ b/include/pugl/detail/win.h
@@ -19,6 +19,9 @@
    @brief Shared definitions for Windows implementation.
 */
 
+#ifndef PUGL_DETAIL_WIN_H
+#define PUGL_DETAIL_WIN_H
+
 #include "pugl/detail/implementation.h"
 
 #include <windows.h>
@@ -145,3 +148,5 @@ puglWinStubEnter(PuglView* view, const PuglEventExpose* expose);
 
 PuglStatus
 puglWinStubLeave(PuglView* view, const PuglEventExpose* expose);
+
+#endif // PUGL_DETAIL_WIN_H
diff --git a/include/pugl/detail/x11.h b/include/pugl/detail/x11.h
index b5ca75c..9788191 100644
--- a/include/pugl/detail/x11.h
+++ b/include/pugl/detail/x11.h
@@ -19,6 +19,9 @@
    @brief Shared definitions for X11 implementation.
 */
 
+#ifndef PUGL_DETAIL_X11_H
+#define PUGL_DETAIL_X11_H
+
 #include "pugl/detail/types.h"
 #include "pugl/pugl.h"
 
@@ -74,3 +77,5 @@ struct PuglInternalsImpl {
 };
 
 PuglStatus puglX11StubConfigure(PuglView* view);
+
+#endif // PUGL_DETAIL_X11_H