diff --git a/Alignment/APEEstimation/interface/EventVariables.h b/Alignment/APEEstimation/interface/EventVariables.h
index 8f9d861de7919..b64541724c7c1 100644
--- a/Alignment/APEEstimation/interface/EventVariables.h
+++ b/Alignment/APEEstimation/interface/EventVariables.h
@@ -1,6 +1,7 @@
 #ifndef Alignment_APEEstimation_EventVariables_h
 #define Alignment_APEEstimation_EventVariables_h
 
+#include <vector>
 
 struct TrackStruct{