diff --git a/core/installer/schema.go b/core/installer/schema.go
index b48217f..2b150a6 100644
--- a/core/installer/schema.go
+++ b/core/installer/schema.go
@@ -376,7 +376,7 @@
 func ExtractDefaultValues(v cue.Value) (any, error) {
 	switch v.IncompleteKind() {
 	case cue.StringKind:
-		if d, ok := v.Default(); ok {
+		if d, ok := v.Default(); ok || d.IsConcrete() {
 			return d.String()
 		}
 	case cue.BoolKind:
@@ -399,8 +399,6 @@
 			return nil, nil
 		} else if isAuth(v) {
 			return nil, nil
-		} else if isSSHKey(v) {
-			return nil, nil
 		} else if isCluster(v) {
 			return nil, nil
 		}
@@ -414,7 +412,12 @@
 			if err != nil {
 				return nil, err
 			}
-			ret[f.Selector().String()] = fv
+			if fv != nil {
+				ret[f.Selector().String()] = fv
+			}
+		}
+		if len(ret) == 0 {
+			return nil, nil
 		}
 		return ret, nil
 	default: