diff --git a/aegisub/src/include/aegisub/exception.h b/aegisub/src/include/aegisub/exception.h
index 737a0312c..cce6d4f06 100644
--- a/aegisub/src/include/aegisub/exception.h
+++ b/aegisub/src/include/aegisub/exception.h
@@ -34,6 +34,7 @@
 /// @ingroup main_headers
 ///
 
+#pragma once
 
 #ifndef AGI_PRE
 #include <wx/string.h>