diff --git a/modules/io/src/io_exception.hh b/modules/io/src/io_exception.hh
index 483f98bca513a200aa6be6034c0229f85225993a..6d8db50cb680f0b0582363863cdabac63d6bf5c6 100644
--- a/modules/io/src/io_exception.hh
+++ b/modules/io/src/io_exception.hh
@@ -38,6 +38,12 @@ public:
     Error(m) {}
 };
 
+class IOFileAlreadyLoadedException: public Error {
+public:
+  IOFileAlreadyLoadedException(const String& m):
+    Error(m) {}
+};
+
 }} // ns
 
 #endif