diff --git a/pkg/functions/function.go b/pkg/functions/function.go
index 86c96321ba..cc17a6f273 100644
--- a/pkg/functions/function.go
+++ b/pkg/functions/function.go
@@ -862,6 +862,9 @@ func (f Function) ImageNameWithDigest(newDigest string) string {
 		return f.Build.Image
 	}
 	image := f.Build.Image
+	if image == "" {
+		return ""
+	}
 
 	// overwrite current digest
 	shaIndex := strings.Index(image, "@sha256:")