diff --git a/src/lib/asiodns/io_fetch.h b/src/lib/asiodns/io_fetch.h
index 9626ffe979..ee0aacd03c 100644
--- a/src/lib/asiodns/io_fetch.h
+++ b/src/lib/asiodns/io_fetch.h
@@ -35,7 +35,7 @@ namespace isc {
 namespace asiodns {
 
 // Forward declarations
-class IOFetchData;
+struct IOFetchData;
 
 /// \brief Upstream Fetch Processing
 ///