diff --git a/source/blender/blenlib/BLI_threads.h b/source/blender/blenlib/BLI_threads.h
index 00d8131d813..8826e9a9936 100644
--- a/source/blender/blenlib/BLI_threads.h
+++ b/source/blender/blenlib/BLI_threads.h
@@ -70,6 +70,7 @@ int		BLI_system_thread_count(void); /* gets the number of threads the system can
 #define LOCK_CUSTOM1	3
 #define LOCK_RCACHE		4
 #define LOCK_OPENGL		5
+#define LOCK_NODES		6
 
 void	BLI_lock_thread(int type);
 void	BLI_unlock_thread(int type);
diff --git a/source/blender/blenlib/intern/threads.c b/source/blender/blenlib/intern/threads.c
index c049ab85546..7b156a3ac52 100644
--- a/source/blender/blenlib/intern/threads.c
+++ b/source/blender/blenlib/intern/threads.c
@@ -113,6 +113,7 @@ static pthread_mutex_t _viewer_lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t _custom1_lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t _rcache_lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_mutex_t _opengl_lock = PTHREAD_MUTEX_INITIALIZER;
+static pthread_mutex_t _nodes_lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_t mainid;
 static int thread_levels= 0;	/* threads can be invoked inside threads */
 
@@ -347,6 +348,8 @@ void BLI_lock_thread(int type)
 		pthread_mutex_lock(&_rcache_lock);
 	else if (type==LOCK_OPENGL)
 		pthread_mutex_lock(&_opengl_lock);
+	else if (type==LOCK_NODES)
+		pthread_mutex_lock(&_nodes_lock);
 }
 
 void BLI_unlock_thread(int type)
@@ -363,6 +366,8 @@ void BLI_unlock_thread(int type)
 		pthread_mutex_unlock(&_rcache_lock);
 	else if(type==LOCK_OPENGL)
 		pthread_mutex_unlock(&_opengl_lock);
+	else if(type==LOCK_NODES)
+		pthread_mutex_unlock(&_nodes_lock);
 }
 
 /* Mutex Locks */
diff --git a/source/blender/nodes/shader/node_shader_tree.c b/source/blender/nodes/shader/node_shader_tree.c
index cc8e1619570..a83b32097df 100644
--- a/source/blender/nodes/shader/node_shader_tree.c
+++ b/source/blender/nodes/shader/node_shader_tree.c
@@ -212,8 +212,15 @@ void ntreeShaderExecTree(bNodeTree *ntree, ShadeInput *shi, ShadeResult *shr)
 	/* each material node has own local shaderesult, with optional copying */
 	memset(shr, 0, sizeof(ShadeResult));
 	
-	if (!exec)
-		exec = ntree->execdata = ntreeShaderBeginExecTree(ntree, 1);
+	/* ensure execdata is only initialized once */
+	if (!exec) {
+		BLI_lock_thread(LOCK_NODES);
+		if(!ntree->execdata)
+			ntree->execdata = ntreeShaderBeginExecTree(ntree, 1);
+		BLI_unlock_thread(LOCK_NODES);
+
+		exec = ntree->execdata;
+	}
 	
 	nts= ntreeGetThreadStack(exec, shi->thread);
 	ntreeExecThreadNodes(exec, nts, &scd, shi->thread);
diff --git a/source/blender/nodes/texture/node_texture_tree.c b/source/blender/nodes/texture/node_texture_tree.c
index 78792956684..5e5d44540dc 100644
--- a/source/blender/nodes/texture/node_texture_tree.c
+++ b/source/blender/nodes/texture/node_texture_tree.c
@@ -232,8 +232,15 @@ int ntreeTexExecTree(
 	data.mtex= mtex;
 	data.shi= shi;
 	
-	if (!exec)
-		exec = ntreeTexBeginExecTree(nodes, 1);
+	/* ensure execdata is only initialized once */
+	if (!exec) {
+		BLI_lock_thread(LOCK_NODES);
+		if(!nodes->execdata)
+			ntreeTexBeginExecTree(nodes, 1);
+		BLI_unlock_thread(LOCK_NODES);
+
+		exec= nodes->execdata;
+	}
 	
 	nts= ntreeGetThreadStack(exec, thread);
 	ntreeExecThreadNodes(exec, nts, &data, thread);