diff --git a/src/kits/interface/layouter/LayoutOptimizer.h b/src/kits/interface/layouter/LayoutOptimizer.h
index 84bdec625d..5919b87867 100644
--- a/src/kits/interface/layouter/LayoutOptimizer.h
+++ b/src/kits/interface/layouter/LayoutOptimizer.h
@@ -6,7 +6,7 @@
 #define LAYOUT_OPTIMIZER_H
 
 #include <List.h>
-
+#include <math.h>
 
 static const double kEqualsEpsilon = 0.000001;