diff --git a/proc_master.go b/proc_master.go
index 767d2f8..e2be659 100644
--- a/proc_master.go
+++ b/proc_master.go
@@ -144,9 +144,11 @@ func (mp *master) handleSignal(s os.Signal) {
 }
 
 func (mp *master) sendSignal(s os.Signal) {
-	if err := mp.slaveCmd.Process.Signal(s); err != nil {
-		mp.debugf("signal failed (%s), assuming slave process died unexpectedly", err)
-		os.Exit(1)
+	if mp.slaveCmd != nil && mp.slaveCmd.Process != nil {
+		if err := mp.slaveCmd.Process.Signal(s); err != nil {
+			mp.debugf("signal failed (%s), assuming slave process died unexpectedly", err)
+			os.Exit(1)
+		}
 	}
 }