diff --git a/src/runtime/mbarrier.go b/src/runtime/mbarrier.go
index c3b45415a9533..efe6c4f2d6346 100644
--- a/src/runtime/mbarrier.go
+++ b/src/runtime/mbarrier.go
@@ -311,6 +311,8 @@ func reflect_typedslicecopy(elemType *_type, dst, src slice) int {
 // If the caller knows that typ has pointers, it can alternatively
 // call memclrHasPointers.
 //
+// TODO: A "go:nosplitrec" annotation would be perfect for this.
+//
 //go:nosplit
 func typedmemclr(typ *_type, ptr unsafe.Pointer) {
 	if writeBarrier.needed && typ.ptrdata != 0 {
diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go
index c8a6cd29362e9..995cb2ae9c2cc 100644
--- a/src/runtime/mheap.go
+++ b/src/runtime/mheap.go
@@ -362,10 +362,17 @@ type mSpanStateBox struct {
 	s atomic.Uint8
 }
 
+// It is nosplit to match get, below.
+
+//go:nosplit
 func (b *mSpanStateBox) set(s mSpanState) {
 	b.s.Store(uint8(s))
 }
 
+// It is nosplit because it's called indirectly by typedmemclr,
+// which must not be preempted.
+
+//go:nosplit
 func (b *mSpanStateBox) get() mSpanState {
 	return mSpanState(b.s.Load())
 }