diff --git a/src/akonadi/akonadiserializer.cpp b/src/akonadi/akonadiserializer.cpp
--- a/src/akonadi/akonadiserializer.cpp
+++ b/src/akonadi/akonadiserializer.cpp
@@ -369,7 +369,7 @@
 
     } else if (isNoteItem(item)) {
         auto note = item.payload<KMime::Message::Ptr>();
-        note->removeHeader("X-Zanshin-RelatedProjectUid");
+        (void)note->removeHeader("X-Zanshin-RelatedProjectUid");
         const QByteArray parentUid = project->property("todoUid").toString().toUtf8();
         if (!parentUid.isEmpty()) {
             auto relatedHeader = new KMime::Headers::Generic("X-Zanshin-RelatedProjectUid");
diff --git a/tests/testlib/gennote.cpp b/tests/testlib/gennote.cpp
--- a/tests/testlib/gennote.cpp
+++ b/tests/testlib/gennote.cpp
@@ -75,7 +75,7 @@
         relatedHeader->from7BitString(uid.toUtf8());
         message->appendHeader(relatedHeader);
     } else {
-        message->removeHeader("X-Zanshin-RelatedProjectUid");
+        (void)message->removeHeader("X-Zanshin-RelatedProjectUid");
     }
     message->assemble();
     m_item.setPayload(message);