diff --git a/alliance/src/a2sdf/src/TimingCell.h b/alliance/src/a2sdf/src/TimingCell.h
index 87f42e37..64f9859a 100644
--- a/alliance/src/a2sdf/src/TimingCell.h
+++ b/alliance/src/a2sdf/src/TimingCell.h
@@ -1,6 +1,7 @@
 #ifndef __TIMING_CELL_H
 #define __TIMING_CELL_H
 
+#include <string>
 #include <iostream>
 #include <fstream>
 #include <map>