diff --git a/src/internal/weak/pointer_test.go b/src/internal/weak/pointer_test.go
index e143749230f0a..5a861bb9ca39d 100644
--- a/src/internal/weak/pointer_test.go
+++ b/src/internal/weak/pointer_test.go
@@ -5,9 +5,12 @@
 package weak_test
 
 import (
+	"context"
 	"internal/weak"
 	"runtime"
+	"sync"
 	"testing"
+	"time"
 )
 
 type T struct {
@@ -128,3 +131,82 @@ func TestPointerFinalizer(t *testing.T) {
 		t.Errorf("weak pointer is non-nil even after finalization: %v", wt)
 	}
 }
+
+// Regression test for issue 69210.
+//
+// Weak-to-strong conversions must shade the new strong pointer, otherwise
+// that might be creating the only strong pointer to a white object which
+// is hidden in a blackened stack.
+//
+// Never fails if correct, fails with some high probability if incorrect.
+func TestIssue69210(t *testing.T) {
+	if testing.Short() {
+		t.Skip("this is a stress test that takes seconds to run on its own")
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
+	defer cancel()
+
+	// What we're trying to do is manufacture the conditions under which this
+	// bug happens. Specifically, we want:
+	//
+	// 1. To create a whole bunch of objects that are only weakly-pointed-to,
+	// 2. To call Strong while the GC is in the mark phase,
+	// 3. The new strong pointer to be missed by the GC,
+	// 4. The following GC cycle to mark a free object.
+	//
+	// Unfortunately, (2) and (3) are hard to control, but we can increase
+	// the likelihood by having several goroutines do (1) at once while
+	// another goroutine constantly keeps us in the GC with runtime.GC.
+	// Like throwing darts at a dart board until they land just right.
+	// We can increase the likelihood of (4) by adding some delay after
+	// creating the strong pointer, but only if it's non-nil. If it's nil,
+	// that means it was already collected in which case there's no chance
+	// of triggering the bug, so we want to retry as fast as possible.
+	// Our heap here is tiny, so the GCs will go by fast.
+	//
+	// As of 2024-09-03, removing the line that shades pointers during
+	// the weak-to-strong conversion causes this test to fail about 50%
+	// of the time.
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for {
+			runtime.GC()
+
+			select {
+			case <-ctx.Done():
+				return
+			default:
+			}
+		}
+	}()
+	for range max(runtime.GOMAXPROCS(-1)-1, 1) {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for {
+				for range 5 {
+					bt := new(T)
+					wt := weak.Make(bt)
+					bt = nil
+					time.Sleep(1 * time.Millisecond)
+					bt = wt.Strong()
+					if bt != nil {
+						time.Sleep(4 * time.Millisecond)
+						bt.t = bt
+						bt.a = 12
+					}
+					runtime.KeepAlive(bt)
+				}
+				select {
+				case <-ctx.Done():
+					return
+				default:
+				}
+			}
+		}()
+	}
+	wg.Wait()
+}
diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go
index 35fd08af50c3c..a91055387ef35 100644
--- a/src/runtime/mheap.go
+++ b/src/runtime/mheap.go
@@ -2073,7 +2073,22 @@ func internal_weak_runtime_makeStrongFromWeak(u unsafe.Pointer) unsafe.Pointer {
 	// Even if we just swept some random span that doesn't contain this object, because
 	// this object is long dead and its memory has since been reused, we'll just observe nil.
 	ptr := unsafe.Pointer(handle.Load())
+
+	// This is responsible for maintaining the same GC-related
+	// invariants as the Yuasa part of the write barrier. During
+	// the mark phase, it's possible that we just created the only
+	// valid pointer to the object pointed to by ptr. If it's only
+	// ever referenced from our stack, and our stack is blackened
+	// already, we could fail to mark it. So, mark it now.
+	if gcphase != _GCoff {
+		shade(uintptr(ptr))
+	}
 	releasem(mp)
+
+	// Explicitly keep ptr alive. This seems unnecessary since we return ptr,
+	// but let's be explicit since it's important we keep ptr alive across the
+	// call to shade.
+	KeepAlive(ptr)
 	return ptr
 }
 
@@ -2081,6 +2096,9 @@ func internal_weak_runtime_makeStrongFromWeak(u unsafe.Pointer) unsafe.Pointer {
 func getOrAddWeakHandle(p unsafe.Pointer) *atomic.Uintptr {
 	// First try to retrieve without allocating.
 	if handle := getWeakHandle(p); handle != nil {
+		// Keep p alive for the duration of the function to ensure
+		// that it cannot die while we're trying to do this.
+		KeepAlive(p)
 		return handle
 	}
 
@@ -2105,6 +2123,10 @@ func getOrAddWeakHandle(p unsafe.Pointer) *atomic.Uintptr {
 			scanblock(uintptr(unsafe.Pointer(&s.handle)), goarch.PtrSize, &oneptrmask[0], gcw, nil)
 			releasem(mp)
 		}
+
+		// Keep p alive for the duration of the function to ensure
+		// that it cannot die while we're trying to do this.
+		KeepAlive(p)
 		return s.handle
 	}
 
@@ -2124,7 +2146,7 @@ func getOrAddWeakHandle(p unsafe.Pointer) *atomic.Uintptr {
 	}
 
 	// Keep p alive for the duration of the function to ensure
-	// that it cannot die while we're trying to this.
+	// that it cannot die while we're trying to do this.
 	KeepAlive(p)
 	return handle
 }
@@ -2154,6 +2176,9 @@ func getWeakHandle(p unsafe.Pointer) *atomic.Uintptr {
 	unlock(&span.speciallock)
 	releasem(mp)
 
+	// Keep p alive for the duration of the function to ensure
+	// that it cannot die while we're trying to do this.
+	KeepAlive(p)
 	return handle
 }