diff --git a/src/Lib/Polygon/polygon.hxx b/src/Lib/Polygon/polygon.hxx
index f7fa2bd5..0517fc7d 100644
--- a/src/Lib/Polygon/polygon.hxx
+++ b/src/Lib/Polygon/polygon.hxx
@@ -30,6 +30,7 @@
 #endif
 
 #include <iostream>
+#include <map>
 #include <string>
 #include <vector>