diff --git a/PhysicsTools/PatExamples/interface/BTagPerformance.h b/PhysicsTools/PatExamples/interface/BTagPerformance.h
index 0ef5b85646e03..1a051474956d4 100644
--- a/PhysicsTools/PatExamples/interface/BTagPerformance.h
+++ b/PhysicsTools/PatExamples/interface/BTagPerformance.h
@@ -12,6 +12,7 @@
 #include "TArrayD.h"
 #include "TGraph.h"
 #include <cassert>
+#include <cmath>
 #include <map>
 
 class BTagPerformance {