diff --git a/src/internal/synctest/synctest_test.go b/src/internal/synctest/synctest_test.go
index 6cebf86c31..307eee62e2 100644
--- a/src/internal/synctest/synctest_test.go
+++ b/src/internal/synctest/synctest_test.go
@@ -383,57 +383,59 @@ func TestChannelMovedOutOfBubble(t *testing.T) {
 	for _, test := range []struct {
 		desc      string
 		f         func(chan struct{})
-		wantPanic string
+		wantFatal string
 	}{{
 		desc: "receive",
 		f: func(ch chan struct{}) {
 			<-ch
 		},
-		wantPanic: "receive on synctest channel from outside bubble",
+		wantFatal: "receive on synctest channel from outside bubble",
 	}, {
 		desc: "send",
 		f: func(ch chan struct{}) {
 			ch <- struct{}{}
 		},
-		wantPanic: "send on synctest channel from outside bubble",
+		wantFatal: "send on synctest channel from outside bubble",
 	}, {
 		desc: "close",
 		f: func(ch chan struct{}) {
 			close(ch)
 		},
-		wantPanic: "close of synctest channel from outside bubble",
+		wantFatal: "close of synctest channel from outside bubble",
 	}} {
 		t.Run(test.desc, func(t *testing.T) {
 			// Bubbled channel accessed from outside any bubble.
 			t.Run("outside_bubble", func(t *testing.T) {
-				donec := make(chan struct{})
-				ch := make(chan chan struct{})
-				go func() {
-					defer close(donec)
-					defer wantPanic(t, test.wantPanic)
-					test.f(<-ch)
-				}()
-				synctest.Run(func() {
-					ch <- make(chan struct{})
+				wantFatal(t, test.wantFatal, func() {
+					donec := make(chan struct{})
+					ch := make(chan chan struct{})
+					go func() {
+						defer close(donec)
+						test.f(<-ch)
+					}()
+					synctest.Run(func() {
+						ch <- make(chan struct{})
+					})
+					<-donec
 				})
-				<-donec
 			})
 			// Bubbled channel accessed from a different bubble.
 			t.Run("different_bubble", func(t *testing.T) {
-				donec := make(chan struct{})
-				ch := make(chan chan struct{})
-				go func() {
-					defer close(donec)
-					c := <-ch
+				wantFatal(t, test.wantFatal, func() {
+					donec := make(chan struct{})
+					ch := make(chan chan struct{})
+					go func() {
+						defer close(donec)
+						c := <-ch
+						synctest.Run(func() {
+							test.f(c)
+						})
+					}()
 					synctest.Run(func() {
-						defer wantPanic(t, test.wantPanic)
-						test.f(c)
+						ch <- make(chan struct{})
 					})
-				}()
-				synctest.Run(func() {
-					ch <- make(chan struct{})
+					<-donec
 				})
-				<-donec
 			})
 		})
 	}
@@ -443,39 +445,40 @@ func TestTimerFromInsideBubble(t *testing.T) {
 	for _, test := range []struct {
 		desc      string
 		f         func(tm *time.Timer)
-		wantPanic string
+		wantFatal string
 	}{{
 		desc: "read channel",
 		f: func(tm *time.Timer) {
 			<-tm.C
 		},
-		wantPanic: "receive on synctest channel from outside bubble",
+		wantFatal: "receive on synctest channel from outside bubble",
 	}, {
 		desc: "Reset",
 		f: func(tm *time.Timer) {
 			tm.Reset(1 * time.Second)
 		},
-		wantPanic: "reset of synctest timer from outside bubble",
+		wantFatal: "reset of synctest timer from outside bubble",
 	}, {
 		desc: "Stop",
 		f: func(tm *time.Timer) {
 			tm.Stop()
 		},
-		wantPanic: "stop of synctest timer from outside bubble",
+		wantFatal: "stop of synctest timer from outside bubble",
 	}} {
 		t.Run(test.desc, func(t *testing.T) {
-			donec := make(chan struct{})
-			ch := make(chan *time.Timer)
-			go func() {
-				defer close(donec)
-				defer wantPanic(t, test.wantPanic)
-				test.f(<-ch)
-			}()
-			synctest.Run(func() {
-				tm := time.NewTimer(1 * time.Second)
-				ch <- tm
+			wantFatal(t, test.wantFatal, func() {
+				donec := make(chan struct{})
+				ch := make(chan *time.Timer)
+				go func() {
+					defer close(donec)
+					test.f(<-ch)
+				}()
+				synctest.Run(func() {
+					tm := time.NewTimer(1 * time.Second)
+					ch <- tm
+				})
+				<-donec
 			})
-			<-donec
 		})
 	}
 }
diff --git a/src/runtime/chan.go b/src/runtime/chan.go
index bb554ebfdb..639d29dc83 100644
--- a/src/runtime/chan.go
+++ b/src/runtime/chan.go
@@ -191,7 +191,7 @@ func chansend(c *hchan, ep unsafe.Pointer, block bool, callerpc uintptr) bool {
 	}
 
 	if c.bubble != nil && getg().bubble != c.bubble {
-		panic(plainError("send on synctest channel from outside bubble"))
+		fatal("send on synctest channel from outside bubble")
 	}
 
 	// Fast path: check for failed non-blocking operation without acquiring the lock.
@@ -318,7 +318,7 @@ func chansend(c *hchan, ep unsafe.Pointer, block bool, callerpc uintptr) bool {
 func send(c *hchan, sg *sudog, ep unsafe.Pointer, unlockf func(), skip int) {
 	if c.bubble != nil && getg().bubble != c.bubble {
 		unlockf()
-		panic(plainError("send on synctest channel from outside bubble"))
+		fatal("send on synctest channel from outside bubble")
 	}
 	if raceenabled {
 		if c.dataqsiz == 0 {
@@ -416,7 +416,7 @@ func closechan(c *hchan) {
 		panic(plainError("close of nil channel"))
 	}
 	if c.bubble != nil && getg().bubble != c.bubble {
-		panic(plainError("close of synctest channel from outside bubble"))
+		fatal("close of synctest channel from outside bubble")
 	}
 
 	lock(&c.lock)
@@ -538,7 +538,7 @@ func chanrecv(c *hchan, ep unsafe.Pointer, block bool) (selected, received bool)
 	}
 
 	if c.bubble != nil && getg().bubble != c.bubble {
-		panic(plainError("receive on synctest channel from outside bubble"))
+		fatal("receive on synctest channel from outside bubble")
 	}
 
 	if c.timer != nil {
@@ -702,7 +702,7 @@ func chanrecv(c *hchan, ep unsafe.Pointer, block bool) (selected, received bool)
 func recv(c *hchan, sg *sudog, ep unsafe.Pointer, unlockf func(), skip int) {
 	if c.bubble != nil && getg().bubble != c.bubble {
 		unlockf()
-		panic(plainError("receive on synctest channel from outside bubble"))
+		fatal("receive on synctest channel from outside bubble")
 	}
 	if c.dataqsiz == 0 {
 		if raceenabled {
diff --git a/src/runtime/select.go b/src/runtime/select.go
index ae7754b173..113dc8ad19 100644
--- a/src/runtime/select.go
+++ b/src/runtime/select.go
@@ -178,7 +178,7 @@ func selectgo(cas0 *scase, order0 *uint16, pc0 *uintptr, nsends, nrecvs int, blo
 
 		if cas.c.bubble != nil {
 			if getg().bubble != cas.c.bubble {
-				panic(plainError("select on synctest channel from outside bubble"))
+				fatal("select on synctest channel from outside bubble")
 			}
 		} else {
 			allSynctest = false
diff --git a/src/runtime/time.go b/src/runtime/time.go
index 4880dce8cd..e9d1f0b6c9 100644
--- a/src/runtime/time.go
+++ b/src/runtime/time.go
@@ -415,7 +415,7 @@ func newTimer(when, period int64, f func(arg any, seq uintptr, delay int64), arg
 //go:linkname stopTimer time.stopTimer
 func stopTimer(t *timeTimer) bool {
 	if t.isFake && getg().bubble == nil {
-		panic("stop of synctest timer from outside bubble")
+		fatal("stop of synctest timer from outside bubble")
 	}
 	return t.stop()
 }
@@ -430,7 +430,7 @@ func resetTimer(t *timeTimer, when, period int64) bool {
 		racerelease(unsafe.Pointer(&t.timer))
 	}
 	if t.isFake && getg().bubble == nil {
-		panic("reset of synctest timer from outside bubble")
+		fatal("reset of synctest timer from outside bubble")
 	}
 	return t.reset(when, period)
 }