diff --git a/srcpkgs/swiften/patches/glibc-2.26-assert.patch b/srcpkgs/swiften/patches/glibc-2.26-assert.patch
new file mode 100644
index 0000000000..2be5c84d6d
--- /dev/null
+++ b/srcpkgs/swiften/patches/glibc-2.26-assert.patch
@@ -0,0 +1,70 @@
+--- Swiften/Avatars/AvatarManagerImpl.cpp.orig	2016-02-26 16:48:56.000000000 +0000
++++ Swiften/Avatars/AvatarManagerImpl.cpp	2017-09-22 19:52:58.365265262 +0000
+@@ -58,7 +58,7 @@
+ 
+ void AvatarManagerImpl::handleCombinedAvatarChanged(const JID& jid) {
+ 	boost::optional<std::string> hash = combinedAvatarProvider.getAvatarHash(jid);
+-	assert(hash);
++	assert(static_cast<bool>(hash));
+ 	offlineAvatarManager->setAvatar(jid, *hash);
+ 	onAvatarChanged(jid);
+ }
+--- Swiften/Parser/PayloadParsers/StorageParser.cpp.orig	2016-02-26 16:48:56.000000000 +0000
++++ Swiften/Parser/PayloadParsers/StorageParser.cpp	2017-09-22 19:59:20.339284968 +0000
+@@ -16,14 +16,14 @@
+ void StorageParser::handleStartElement(const std::string& element, const std::string&, const AttributeMap& attributes) {
+ 	if (level == BookmarkLevel) {
+ 		if (element == "conference") {
+-			assert(!room);
++			assert(!static_cast<bool>(room));
+ 			room = Storage::Room();
+ 			room->autoJoin = attributes.getBoolAttribute("autojoin", false);
+ 			room->jid = JID(attributes.getAttribute("jid"));
+ 			room->name = attributes.getAttribute("name");
+ 		}
+ 		else if (element == "url") {
+-			assert(!url);
++			assert(!static_cast<bool>(url));
+ 			url = Storage::URL();
+ 			url->name = attributes.getAttribute("name");
+ 			url->url = attributes.getAttribute("url");
+@@ -39,12 +39,12 @@
+ 	--level;
+ 	if (level == BookmarkLevel) {
+ 		if (element == "conference") {
+-			assert(room);
++			assert(static_cast<bool>(room));
+ 			getPayloadInternal()->addRoom(*room);
+ 			room.reset();
+ 		}
+ 		else if (element == "url") {
+-			assert(url);
++			assert(static_cast<bool>(url));
+ 			getPayloadInternal()->addURL(*url);
+ 			url.reset();
+ 		}
+--- Swiften/Parser/PayloadParsers/SearchPayloadParser.cpp.orig	2016-02-26 16:48:56.000000000 +0000
++++ Swiften/Parser/PayloadParsers/SearchPayloadParser.cpp	2017-09-22 20:08:46.417314171 +0000
+@@ -26,11 +26,11 @@
+ 	}
+ 	else if (level == PayloadLevel) {
+ 		if (element == "x" && ns == "jabber:x:data") {
+-			assert(!formParser);
++			assert(!static_cast<bool>(formParser));
+ 			formParser = boost::polymorphic_downcast<FormParser*>(formParserFactory->createPayloadParser());
+ 		}
+ 		else if (element == "item") {
+-			assert(!currentItem);
++			assert(!static_cast<bool>(currentItem));
+ 			currentItem.reset(SearchPayload::Item());
+ 			currentItem->jid = JID(attributes.getAttribute("jid"));
+ 		}
+@@ -65,7 +65,7 @@
+ 			formParser = NULL;
+ 		}
+ 		else if (element == "item") {
+-			assert(currentItem);
++			assert(static_cast<bool>(currentItem));
+ 			getPayloadInternal()->addItem(*currentItem);
+ 			currentItem.reset();
+ 		}