diff --git a/git-codereview/doc.go b/git-codereview/doc.go
index 4be0c0d..0754479 100644
--- a/git-codereview/doc.go
+++ b/git-codereview/doc.go
@@ -256,6 +256,9 @@
 
 The -trybot flag sets a Run-TryBot+1 vote on any uploaded changes.
 The Go project uses this vote to start running integration tests on the CL.
+During the transition between two CI systems, the environment variable
+GIT_CODEREVIEW_TRYBOT can be set to one of "luci", "farmer", or "both"
+to explicitly override where the -trybot flag starts integration tests.
 
 The -autosubmit flag sets a Auto-Submit+1 vote on any uploaded changes.
 
diff --git a/git-codereview/mail.go b/git-codereview/mail.go
index 5d385f9..4bcd85c 100644
--- a/git-codereview/mail.go
+++ b/git-codereview/mail.go
@@ -6,6 +6,7 @@
 
 import (
 	"fmt"
+	"os"
 	"regexp"
 	"sort"
 	"strings"
@@ -47,6 +48,19 @@
 		exit(2)
 	}
 
+	var trybotVotes []string
+	switch os.Getenv("GIT_CODEREVIEW_TRYBOT") {
+	case "luci":
+		trybotVotes = []string{"Commit-Queue+1"}
+	case "", "farmer":
+		trybotVotes = []string{"Run-TryBot"}
+	case "both":
+		trybotVotes = []string{"Commit-Queue+1", "Run-TryBot"}
+	default:
+		fmt.Fprintf(stderr(), "GIT_CODEREVIEW_TRYBOT must be unset, blank, or one of 'luci', 'farmer', or 'both'\n")
+		exit(2)
+	}
+
 	b := CurrentBranch()
 
 	var c *Commit
@@ -142,8 +156,10 @@
 		start = ","
 	}
 	if *trybot {
-		refSpec += start + "l=Run-TryBot"
-		start = ","
+		for _, v := range trybotVotes {
+			refSpec += start + "l=" + v
+			start = ","
+		}
 	}
 	if *wip {
 		refSpec += start + "wip"