diff --git a/cmd/apidiff/main.go b/cmd/apidiff/main.go
index 552062e..7cc0caf 100644
--- a/cmd/apidiff/main.go
+++ b/cmd/apidiff/main.go
@@ -92,6 +92,9 @@
 	if err != nil {
 		return nil, err
 	}
+	if len(pkgs) == 0 {
+		return nil, fmt.Errorf("found no packages for import %s", importPath)
+	}
 	if len(pkgs[0].Errors) > 0 {
 		return nil, pkgs[0].Errors[0]
 	}