diff --git a/finish.go b/finish.go
index b66bf30..80b6306 100644
--- a/finish.go
+++ b/finish.go
@@ -12,6 +12,12 @@ type FinishJobRequest struct {
 	JobUUID    string `json:"-"`
 	ExitStatus int    `json:"exit_status,omitempty"`
 	Detail     string `json:"detail"`
+	// SignalReason optionally records why the stack terminated the job (for
+	// example "stack_error"), giving the job a machine-readable failure
+	// reason alongside the human-readable Detail. Known values match the
+	// signal reasons documented for retry rules:
+	// https://buildkite.com/docs/pipelines/configure/retry
+	SignalReason string `json:"signal_reason,omitempty"`
 }
 
 func (c *Client) FinishJob(ctx context.Context, finishJobReq FinishJobRequest, opts ...RequestOption) (http.Header, error) {
diff --git a/finish_test.go b/finish_test.go
index cfb7e7a..f78cea5 100644
--- a/finish_test.go
+++ b/finish_test.go
@@ -25,8 +25,9 @@ func TestFinishJob(t *testing.T) {
 			}
 
 			expectedParams := FinishJobRequest{
-				ExitStatus: -10,
-				Detail:     "show me the money",
+				ExitStatus:   -10,
+				Detail:       "show me the money",
+				SignalReason: "stack_error",
 			}
 
 			if diff := cmp.Diff(expectedParams, params); diff != "" {
@@ -39,10 +40,11 @@ func TestFinishJob(t *testing.T) {
 		t.Cleanup(func() { server.Close() })
 
 		req := FinishJobRequest{
-			StackKey:   "stack-123",
-			JobUUID:    "456",
-			ExitStatus: -10,
-			Detail:     "show me the money",
+			StackKey:     "stack-123",
+			JobUUID:      "456",
+			ExitStatus:   -10,
+			Detail:       "show me the money",
+			SignalReason: "stack_error",
 		}
 
 		header, err := client.FinishJob(t.Context(), req)