diff --git a/engine/graph/actions.go b/engine/graph/actions.go
index 85b23a05..58c8313c 100644
--- a/engine/graph/actions.go
+++ b/engine/graph/actions.go
@@ -41,14 +41,18 @@ func (obj *Engine) OKTimestamp(vertex pgraph.Vertex) bool {
 // be bad.
 func (obj *Engine) BadTimestamps(vertex pgraph.Vertex) []pgraph.Vertex {
 	vs := []pgraph.Vertex{}
-	ts := obj.state[vertex].timestamp
+	obj.state[vertex].mutex.RLock()   // concurrent read start
+	ts := obj.state[vertex].timestamp // race
+	obj.state[vertex].mutex.RUnlock() // concurrent read end
 	// these are all the vertices pointing TO vertex, eg: ??? -> vertex
 	for _, v := range obj.graph.IncomingGraphVertices(vertex) {
 		// If the vertex has a greater timestamp than any prerequisite,
 		// then we can't run right now. If they're equal (eg: initially
 		// with a value of 0) then we also can't run because we should
 		// let our pre-requisites go first.
-		t := obj.state[v].timestamp
+		obj.state[v].mutex.RLock()   // concurrent read start
+		t := obj.state[v].timestamp  // race
+		obj.state[v].mutex.RUnlock() // concurrent read end
 		if obj.Debug {
 			obj.Logf("OKTimestamp: %d >= %d (%s): !%t", ts, t, v.String(), ts >= t)
 		}
@@ -132,8 +136,7 @@ func (obj *Engine) Process(ctx context.Context, vertex pgraph.Vertex) error {
 					}
 					// if changed == true, at least one was updated
 					// invalidate cache, mark as dirty
-					obj.state[v].tuid.StopTimer()
-					obj.state[v].isStateOK = false
+					obj.state[v].setDirty()
 					//break // we might have more vertices now
 				}
 
@@ -227,7 +230,9 @@ func (obj *Engine) Process(ctx context.Context, vertex pgraph.Vertex) error {
 		wg := &sync.WaitGroup{}
 		// update this timestamp *before* we poke or the poked
 		// nodes might fail due to having a too old timestamp!
-		obj.state[vertex].timestamp = time.Now().UnixNano() // update timestamp
+		obj.state[vertex].mutex.Lock()                      // concurrent write start
+		obj.state[vertex].timestamp = time.Now().UnixNano() // update timestamp (race)
+		obj.state[vertex].mutex.Unlock()                    // concurrent write end
 		for _, v := range obj.graph.OutgoingGraphVertices(vertex) {
 			if !obj.OKTimestamp(v) {
 				// there is at least another one that will poke this...
diff --git a/engine/graph/state.go b/engine/graph/state.go
index 33cbff10..324e0b9e 100644
--- a/engine/graph/state.go
+++ b/engine/graph/state.go
@@ -64,6 +64,8 @@ type State struct {
 	isStateOK bool  // is state OK or do we need to run CheckApply ?
 	workerErr error // did the Worker error?
 
+	mutex *sync.RWMutex // used for editing state properties
+
 	// doneCtx is cancelled when Watch should shut down. When any of the
 	// following channels close, it causes this to close.
 	doneCtx context.Context
@@ -143,6 +145,7 @@ func (obj *State) Init() error {
 		return fmt.Errorf("the Logf function is missing")
 	}
 
+	obj.mutex = &sync.RWMutex{}
 	obj.doneCtx, obj.doneCtxCancel = context.WithCancel(context.Background())
 
 	obj.processDone = make(chan struct{})
@@ -387,7 +390,9 @@ func (obj *State) event() {
 // CheckApply will have some work to do in order to converge it.
 func (obj *State) setDirty() {
 	obj.tuid.StopTimer()
-	obj.isStateOK = false
+	obj.mutex.Lock()
+	obj.isStateOK = false // concurrent write
+	obj.mutex.Unlock()
 }
 
 // poll is a replacement for Watch when the Poll metaparameter is used.
diff --git a/lang/interpret_test/TestAstFunc3/race.txtar b/lang/interpret_test/TestAstFunc3/race.txtar
new file mode 100644
index 00000000..be2549d7
--- /dev/null
+++ b/lang/interpret_test/TestAstFunc3/race.txtar
@@ -0,0 +1,21 @@
+-- main.mcl --
+# check for timestamp or other state races in the resource engine
+print "print1" {
+	msg => "i am print1",
+
+	Meta:autogroup => false,
+}
+
+print "print2" {
+	msg => "i am print2",
+
+	Meta:autogroup => false,
+
+	Depend => Print["print1"],
+}
+-- OUTPUT --
+Edge: print[print1] -> print[print2] # print[print1] -> print[print2]
+Field: print[print1].Msg = "i am print1"
+Field: print[print2].Msg = "i am print2"
+Vertex: print[print1]
+Vertex: print[print2]