diff --git a/cmd/releasebot/git.go b/cmd/releasebot/git.go
index d79a3a3..9fc975b 100644
--- a/cmd/releasebot/git.go
+++ b/cmd/releasebot/git.go
@@ -18,13 +18,20 @@
 	privateGoRepoURL = "sso://team/golang/go-private"
 )
 
-// gitCheckout sets up a fresh git checkout in which to work,
-// in $HOME/go-releasebot-work/<release>/gitwork
-// (where <release> is a string like go1.8.5).
+// gitCheckout sets w.Dir to the work directory
+// at $HOME/go-releasebot-work/<release> (where <release> is a string like go1.8.5),
+// creating it if it doesn't exist,
+// and sets up a fresh git checkout in which to work,
+// in $HOME/go-releasebot-work/<release>/gitwork.
+//
 // The first time it is run for a particular release,
 // gitCheckout also creates a clean checkout in
 // $HOME/go-releasebot-work/<release>/gitmirror,
 // to use as an object cache to speed future checkouts.
+//
+// For beta releases in -mode=release, it sets w.Dir but doesn't
+// fetch the latest master branch. This way the exact commit that
+// was tested in prepare mode is also used in release mode.
 func (w *Work) gitCheckout() {
 	w.Dir = filepath.Join(os.Getenv("HOME"), "go-releasebot-work/"+strings.ToLower(w.Version))
 	w.log.Printf("working in %s\n", w.Dir)
@@ -32,6 +39,13 @@
 		w.log.Panic(err)
 	}
 
+	if w.BetaRelease && !w.Prepare {
+		// We don't want to fetch the latest "master" branch for
+		// a beta release. Instead, reuse the same commit that was
+		// already fetched from origin and tested in prepare mode.
+		return
+	}
+
 	origin := publicGoRepoURL
 	if w.Security {
 		origin = privateGoRepoURL
diff --git a/cmd/releasebot/main.go b/cmd/releasebot/main.go
index 414bc2a..11939b7 100644
--- a/cmd/releasebot/main.go
+++ b/cmd/releasebot/main.go
@@ -734,10 +734,7 @@
 			// The prepare step will run the tests on a commit that has the same
 			// tree (but maybe different message) as the one that the release
 			// step will process, so we can skip tests the second time.
-			// For beta releases, we're releasing from master. Beta releases
-			// should not skip tests, as a new commit may have been pushed after
-			// the prepare step.
-			if !w.Prepare && !w.BetaRelease {
+			if !w.Prepare {
 				args = append(args, "-skip_tests")
 			}
 			out, err := w.runner(releaseDir, "GOPATH="+filepath.Join(w.Dir, "gopath")).runErr(args...)