Add missing header

diff --git a/saml/signature/ContentReference.h b/saml/signature/ContentReference.h
index a8f1625..9bc9973 100644 (file)
--- a/saml/signature/ContentReference.h
+++ b/saml/signature/ContentReference.h
@@ -26,6 +26,8 @@
 #include <saml/base.h>\r
 #include <xmltooling/signature/ContentReference.h>\r
 \r
+#include <string>\r
+\r
 namespace opensaml {\r
 \r
     class SAML_API SignableObject;\r