diff --git a/include/libcamera/internal/process.h b/include/libcamera/internal/process.h
index 458a2149..254cda85 100644
--- a/include/libcamera/internal/process.h
+++ b/include/libcamera/internal/process.h
@@ -15,6 +15,8 @@
 
 namespace libcamera {
 
+class EventNotifier;
+
 class Process final
 {
 public: