diff --git a/src/runtime/testdata/testprog/traceback_ancestors.go b/src/runtime/testdata/testprog/traceback_ancestors.go
index fe57c1c157..0ee402c4bd 100644
--- a/src/runtime/testdata/testprog/traceback_ancestors.go
+++ b/src/runtime/testdata/testprog/traceback_ancestors.go
@@ -5,8 +5,10 @@
 package main
 
 import (
+	"bytes"
 	"fmt"
 	"runtime"
+	"strings"
 )
 
 func init() {
@@ -18,25 +20,50 @@ const numFrames = 2
 
 func TracebackAncestors() {
 	w := make(chan struct{})
-	recurseThenCallGo(w, numGoroutines, numFrames)
+	recurseThenCallGo(w, numGoroutines, numFrames, true)
 	<-w
 	printStack()
 	close(w)
 }
 
+var ignoreGoroutines = make(map[string]bool)
+
 func printStack() {
 	buf := make([]byte, 1024)
 	for {
 		n := runtime.Stack(buf, true)
 		if n < len(buf) {
-			fmt.Print(string(buf[:n]))
+			tb := string(buf[:n])
+
+			// Delete any ignored goroutines, if present.
+			pos := 0
+			for pos < len(tb) {
+				next := pos + strings.Index(tb[pos:], "\n\n")
+				if next < pos {
+					next = len(tb)
+				} else {
+					next += len("\n\n")
+				}
+
+				if strings.HasPrefix(tb[pos:], "goroutine ") {
+					id := tb[pos+len("goroutine "):]
+					id = id[:strings.IndexByte(id, ' ')]
+					if ignoreGoroutines[id] {
+						tb = tb[:pos] + tb[next:]
+						next = pos
+					}
+				}
+				pos = next
+			}
+
+			fmt.Print(tb)
 			return
 		}
 		buf = make([]byte, 2*len(buf))
 	}
 }
 
-func recurseThenCallGo(w chan struct{}, frames int, goroutines int) {
+func recurseThenCallGo(w chan struct{}, frames int, goroutines int, main bool) {
 	if frames == 0 {
 		// Signal to TracebackAncestors that we are done recursing and starting goroutines.
 		w <- struct{}{}
@@ -44,10 +71,29 @@ func recurseThenCallGo(w chan struct{}, frames int, goroutines int) {
 		return
 	}
 	if goroutines == 0 {
+		// Record which goroutine this is so we can ignore it
+		// in the traceback if it hasn't finished exiting by
+		// the time we printStack.
+		if !main {
+			ignoreGoroutines[goroutineID()] = true
+		}
+
 		// Start the next goroutine now that there are no more recursions left
 		// for this current goroutine.
-		go recurseThenCallGo(w, frames-1, numFrames)
+		go recurseThenCallGo(w, frames-1, numFrames, false)
 		return
 	}
-	recurseThenCallGo(w, frames, goroutines-1)
+	recurseThenCallGo(w, frames, goroutines-1, main)
+}
+
+func goroutineID() string {
+	buf := make([]byte, 128)
+	runtime.Stack(buf, false)
+	const prefix = "goroutine "
+	if !bytes.HasPrefix(buf, []byte(prefix)) {
+		panic(fmt.Sprintf("expected %q at beginning of traceback:\n%s", prefix, buf))
+	}
+	buf = buf[len(prefix):]
+	n := bytes.IndexByte(buf, ' ')
+	return string(buf[:n])
 }