diff --git a/source/blender/compositor/nodes/COM_GroupNode.cpp b/source/blender/compositor/nodes/COM_GroupNode.cpp
index e5255b6bb87..43dcb7be87f 100644
--- a/source/blender/compositor/nodes/COM_GroupNode.cpp
+++ b/source/blender/compositor/nodes/COM_GroupNode.cpp
@@ -37,6 +37,7 @@ void GroupNode::convertToOperations(ExecutionSystem *graph, CompositorContext *c
 void GroupNode::ungroup(ExecutionSystem &system)
 {
 	bNode *bnode = this->getbNode();
+	bNodeTree *subtree = (bNodeTree *)bnode->id;
 	vector<InputSocket *> &inputsockets = this->getInputSockets();
 	vector<OutputSocket *> &outputsockets = this->getOutputSockets();
 	unsigned int index;
@@ -44,6 +45,10 @@ void GroupNode::ungroup(ExecutionSystem &system)
 	/* get the node list size _before_ adding proxy nodes, so they are available for linking */
 	int nodes_start = system.getNodes().size();
 
+	/* missing node group datablock can happen with library linking */
+	if(!subtree)
+		return;
+
 	for (index = 0; index < inputsockets.size(); index++) {
 		InputSocket *inputSocket = inputsockets[index];
 		bNodeSocket *editorInput = inputSocket->getbNodeSocket();
@@ -64,6 +69,5 @@ void GroupNode::ungroup(ExecutionSystem &system)
 		}
 	}
 
-	bNodeTree *subtree = (bNodeTree *)bnode->id;
 	ExecutionSystemHelper::addbNodeTree(system, nodes_start, subtree, bnode);
 }