diff --git a/contrib/ci/qt5-thread-test/qt-thread-test.cpp b/contrib/ci/qt5-thread-test/qt-thread-test.cpp
index 1f2236f09..daa6cb2e4 100644
--- a/contrib/ci/qt5-thread-test/qt-thread-test.cpp
+++ b/contrib/ci/qt5-thread-test/qt-thread-test.cpp
@@ -4,9 +4,7 @@
  * SPDX-License-Identifier: LGPL-2.1+
  */
 
-extern "C" {
 #include <fwupd.h>
-}
 
 #include <QCoreApplication>
 #include <QtConcurrentRun>
diff --git a/libfwupd/fwupd-client-sync.h b/libfwupd/fwupd-client-sync.h
index c7da3033b..9888fd812 100644
--- a/libfwupd/fwupd-client-sync.h
+++ b/libfwupd/fwupd-client-sync.h
@@ -8,6 +8,8 @@
 
 #include "fwupd-client.h"
 
+G_BEGIN_DECLS
+
 gboolean	 fwupd_client_connect			(FwupdClient	*self,
 							 GCancellable	*cancellable,
 							 GError		**error)
@@ -225,3 +227,5 @@ GBytes		*fwupd_client_upload_bytes		(FwupdClient	*self,
 							 GCancellable	*cancellable,
 							 GError		**error)
 							 G_GNUC_WARN_UNUSED_RESULT;
+
+G_END_DECLS