diff --git a/src/runtime/map.go b/src/runtime/map.go
index c03e745dc5..c3fcfbfdbe 100644
--- a/src/runtime/map.go
+++ b/src/runtime/map.go
@@ -567,7 +567,7 @@ func mapassign(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer {
 
 	// Set hashWriting after calling alg.hash, since alg.hash may panic,
 	// in which case we have not actually done a write.
-	h.flags |= hashWriting
+	h.flags ^= hashWriting
 
 	if h.buckets == nil {
 		h.buckets = newobject(t.bucket) // newarray(t.bucket, 1)
@@ -679,7 +679,7 @@ func mapdelete(t *maptype, h *hmap, key unsafe.Pointer) {
 
 	// Set hashWriting after calling alg.hash, since alg.hash may panic,
 	// in which case we have not actually done a write (delete).
-	h.flags |= hashWriting
+	h.flags ^= hashWriting
 
 	bucket := hash & bucketMask(h.B)
 	if h.growing() {
@@ -921,7 +921,7 @@ func mapclear(t *maptype, h *hmap) {
 		throw("concurrent map writes")
 	}
 
-	h.flags |= hashWriting
+	h.flags ^= hashWriting
 
 	h.flags &^= sameSizeGrow
 	h.oldbuckets = nil
diff --git a/src/runtime/map_fast32.go b/src/runtime/map_fast32.go
index bf0b23604b..671558545a 100644
--- a/src/runtime/map_fast32.go
+++ b/src/runtime/map_fast32.go
@@ -103,7 +103,7 @@ func mapassign_fast32(t *maptype, h *hmap, key uint32) unsafe.Pointer {
 	hash := t.key.alg.hash(noescape(unsafe.Pointer(&key)), uintptr(h.hash0))
 
 	// Set hashWriting after calling alg.hash for consistency with mapassign.
-	h.flags |= hashWriting
+	h.flags ^= hashWriting
 
 	if h.buckets == nil {
 		h.buckets = newobject(t.bucket) // newarray(t.bucket, 1)
@@ -189,7 +189,7 @@ func mapassign_fast32ptr(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer
 	hash := t.key.alg.hash(noescape(unsafe.Pointer(&key)), uintptr(h.hash0))
 
 	// Set hashWriting after calling alg.hash for consistency with mapassign.
-	h.flags |= hashWriting
+	h.flags ^= hashWriting
 
 	if h.buckets == nil {
 		h.buckets = newobject(t.bucket) // newarray(t.bucket, 1)
@@ -276,7 +276,7 @@ func mapdelete_fast32(t *maptype, h *hmap, key uint32) {
 	hash := t.key.alg.hash(noescape(unsafe.Pointer(&key)), uintptr(h.hash0))
 
 	// Set hashWriting after calling alg.hash for consistency with mapdelete
-	h.flags |= hashWriting
+	h.flags ^= hashWriting
 
 	bucket := hash & bucketMask(h.B)
 	if h.growing() {
diff --git a/src/runtime/map_fast64.go b/src/runtime/map_fast64.go
index 4bde9e2be0..164a4dd1ce 100644
--- a/src/runtime/map_fast64.go
+++ b/src/runtime/map_fast64.go
@@ -103,7 +103,7 @@ func mapassign_fast64(t *maptype, h *hmap, key uint64) unsafe.Pointer {
 	hash := t.key.alg.hash(noescape(unsafe.Pointer(&key)), uintptr(h.hash0))
 
 	// Set hashWriting after calling alg.hash for consistency with mapassign.
-	h.flags |= hashWriting
+	h.flags ^= hashWriting
 
 	if h.buckets == nil {
 		h.buckets = newobject(t.bucket) // newarray(t.bucket, 1)
@@ -189,7 +189,7 @@ func mapassign_fast64ptr(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer
 	hash := t.key.alg.hash(noescape(unsafe.Pointer(&key)), uintptr(h.hash0))
 
 	// Set hashWriting after calling alg.hash for consistency with mapassign.
-	h.flags |= hashWriting
+	h.flags ^= hashWriting
 
 	if h.buckets == nil {
 		h.buckets = newobject(t.bucket) // newarray(t.bucket, 1)
@@ -276,7 +276,7 @@ func mapdelete_fast64(t *maptype, h *hmap, key uint64) {
 	hash := t.key.alg.hash(noescape(unsafe.Pointer(&key)), uintptr(h.hash0))
 
 	// Set hashWriting after calling alg.hash for consistency with mapdelete
-	h.flags |= hashWriting
+	h.flags ^= hashWriting
 
 	bucket := hash & bucketMask(h.B)
 	if h.growing() {
diff --git a/src/runtime/map_faststr.go b/src/runtime/map_faststr.go
index 415bbff143..bee62dfb03 100644
--- a/src/runtime/map_faststr.go
+++ b/src/runtime/map_faststr.go
@@ -202,7 +202,7 @@ func mapassign_faststr(t *maptype, h *hmap, s string) unsafe.Pointer {
 	hash := t.key.alg.hash(noescape(unsafe.Pointer(&s)), uintptr(h.hash0))
 
 	// Set hashWriting after calling alg.hash for consistency with mapassign.
-	h.flags |= hashWriting
+	h.flags ^= hashWriting
 
 	if h.buckets == nil {
 		h.buckets = newobject(t.bucket) // newarray(t.bucket, 1)
@@ -294,7 +294,7 @@ func mapdelete_faststr(t *maptype, h *hmap, ky string) {
 	hash := t.key.alg.hash(noescape(unsafe.Pointer(&ky)), uintptr(h.hash0))
 
 	// Set hashWriting after calling alg.hash for consistency with mapdelete
-	h.flags |= hashWriting
+	h.flags ^= hashWriting
 
 	bucket := hash & bucketMask(h.B)
 	if h.growing() {