diff --git a/adb/adb.go b/adb/adb.go
index ffd525b..e8399e6 100644
--- a/adb/adb.go
+++ b/adb/adb.go
@@ -157,6 +157,9 @@ func (d *Device) Install(path string) error {
 	if line == "Success" {
 		return nil
 	}
+	if !strings.HasPrefix(line, "Failure [INSTALL_") {
+		return errors.New("unknown result: " + line)
+	}
 	code := line[len("Failure [INSTALL_") : len(line)-1]
 	switch code {
 	case "FAILED_ALREADY_EXISTS":
@@ -267,6 +270,9 @@ func (d *Device) Uninstall(pkg string) error {
 	if line == "Success" {
 		return nil
 	}
+	if !strings.HasPrefix(line, "Failure [DELETE_") {
+		return errors.New("unknown result: " + line)
+	}
 	code := line[len("Failure [DELETE_") : len(line)-1]
 	switch code {
 	case "FAILED_INTERNAL_ERROR":