diff --git a/drone/build/build_info.go b/drone/build/build_info.go
index bc59398..f8c5ccd 100644
--- a/drone/build/build_info.go
+++ b/drone/build/build_info.go
@@ -36,7 +36,7 @@ func buildInfo(c *cli.Context) error {
 	}
 
 	var number int
-	if buildArg == "last" {
+	if buildArg == "last" || len(buildArg) == 0 {
 		// Fetch the build number from the last build
 		build, err := client.BuildLast(owner, name, "")
 		if err != nil {
diff --git a/drone/build/build_start.go b/drone/build/build_start.go
index 4d46612..c986789 100644
--- a/drone/build/build_start.go
+++ b/drone/build/build_start.go
@@ -1,6 +1,7 @@
 package build
 
 import (
+	"errors"
 	"fmt"
 	"strconv"
 
@@ -47,6 +48,9 @@ func buildStart(c *cli.Context) (err error) {
 		}
 		number = build.Number
 	} else {
+		if len(buildArg) == 0 {
+			return errors.New("missing job number")
+		}
 		number, err = strconv.Atoi(buildArg)
 		if err != nil {
 			return err