diff --git a/src/runtime/crash_unix_test.go b/src/runtime/crash_unix_test.go
index 6c42cb9..c50d62d 100644
--- a/src/runtime/crash_unix_test.go
+++ b/src/runtime/crash_unix_test.go
@@ -232,13 +232,20 @@
 	}
 	defer pr.Close()
 
-	// Wait for "x\nx\n" to indicate readiness.
+	// Wait for "x\nx\n" to indicate almost-readiness.
 	buf := make([]byte, 4)
 	_, err = io.ReadFull(pr, buf)
 	if err != nil || string(buf) != "x\nx\n" {
 		t.Fatal("subprocess failed; output:\n", string(buf))
 	}
 
+	// The child blockers print "x\n" and then block on a lock. Receiving
+	// those bytes only indicates that the child is _about to block_. Since
+	// we don't have a way to know when it is fully blocked, sleep a bit to
+	// make us less likely to lose the race and signal before the child
+	// blocks.
+	time.Sleep(100*time.Millisecond)
+
 	// Send SIGQUIT.
 	if err := cmd.Process.Signal(syscall.SIGQUIT); err != nil {
 		t.Fatal("signaling subprocess: ", err)