diff --git a/src/interfaces/libpq++/pgenv.h b/src/interfaces/libpq++/pgenv.h
index 768c5d86b9..4bdc0c94ae 100644
--- a/src/interfaces/libpq++/pgenv.h
+++ b/src/interfaces/libpq++/pgenv.h
@@ -18,7 +18,7 @@
 #ifndef PGENV_H
 #define PGENV_H
 
-#include <string>
+#include <string.h>
 
 
 //