diff --git a/src/runtime/metrics_test.go b/src/runtime/metrics_test.go
index d7f41334cd6b62..586610727563c2 100644
--- a/src/runtime/metrics_test.go
+++ b/src/runtime/metrics_test.go
@@ -1290,3 +1290,38 @@ func (w *contentionWorker) run() {
 	for w.fn() {
 	}
 }
+
+func TestMetricHeapUnusedLargeObjectOverflow(t *testing.T) {
+	// This test makes sure /memory/classes/heap/unused:bytes
+	// doesn't overflow when allocating and deallocating large
+	// objects. It is a regression test for #67019.
+	done := make(chan struct{})
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for {
+			for i := 0; i < 10; i++ {
+				runtime.Escape(make([]byte, 1<<20))
+			}
+			runtime.GC()
+			select {
+			case <-done:
+				return
+			default:
+			}
+		}
+	}()
+	s := []metrics.Sample{
+		{Name: "/memory/classes/heap/unused:bytes"},
+	}
+	for i := 0; i < 1000; i++ {
+		metrics.Read(s)
+		if s[0].Value.Uint64() > 1<<40 {
+			t.Errorf("overflow")
+			break
+		}
+	}
+	done <- struct{}{}
+	wg.Wait()
+}
diff --git a/src/runtime/mgcsweep.go b/src/runtime/mgcsweep.go
index 3dbe9bcec72fb1..35be7949472f8c 100644
--- a/src/runtime/mgcsweep.go
+++ b/src/runtime/mgcsweep.go
@@ -770,6 +770,19 @@ func (sl *sweepLocked) sweep(preserve bool) bool {
 		if nfreed != 0 {
 			// Free large object span to heap.
 
+			// Count the free in the consistent, external stats.
+			//
+			// Do this before freeSpan, which might update heapStats' inHeap
+			// value. If it does so, then metrics that subtract object footprint
+			// from inHeap might overflow. See #67019.
+			stats := memstats.heapStats.acquire()
+			atomic.Xadd64(&stats.largeFreeCount, 1)
+			atomic.Xadd64(&stats.largeFree, int64(size))
+			memstats.heapStats.release()
+
+			// Count the free in the inconsistent, internal stats.
+			gcController.totalFree.Add(int64(size))
+
 			// NOTE(rsc,dvyukov): The original implementation of efence
 			// in CL 22060046 used sysFree instead of sysFault, so that
 			// the operating system would eventually give the memory
@@ -802,16 +815,6 @@ func (sl *sweepLocked) sweep(preserve bool) bool {
 				// invalid pointer. See arena.go:(*mheap).allocUserArenaChunk.
 				*(*uintptr)(unsafe.Pointer(&s.largeType)) = 0
 			}
-
-			// Count the free in the consistent, external stats.
-			stats := memstats.heapStats.acquire()
-			atomic.Xadd64(&stats.largeFreeCount, 1)
-			atomic.Xadd64(&stats.largeFree, int64(size))
-			memstats.heapStats.release()
-
-			// Count the free in the inconsistent, internal stats.
-			gcController.totalFree.Add(int64(size))
-
 			return true
 		}