diff --git a/internal/config/unit.go b/internal/config/unit.go
index d702f60..e7cf3db 100644
--- a/internal/config/unit.go
+++ b/internal/config/unit.go
@@ -58,11 +58,12 @@ func (u *Unit) UnmarshalYAML(value *yaml.Node) error {
 		if err := yaml.Unmarshal(defaults, &m); err != nil {
 			return errors.Wrap(err, "failed to unmarshal defaults")
 		}
-		if err := mergo.Merge(&u.Values, m); err != nil {
+		if err := mergo.Merge(&m, u.Values, mergo.WithAppendSlice, mergo.WithOverride, mergo.WithSliceDeepCopy); err != nil {
 			return err
 		}
 
 		u.Extends = ""
+		u.Values = m
 	}
 	return nil
 }
diff --git a/testdata/extends/snapshop-config-norender.yaml b/testdata/extends/snapshop-config-norender.yaml
index 2028f43..eb99ca9 100644
--- a/testdata/extends/snapshop-config-norender.yaml
+++ b/testdata/extends/snapshop-config-norender.yaml
@@ -14,6 +14,9 @@ squadron:
         image:
           repository: nginx
           tag: latest
+        null_obj: null
+        null_tags: null
         tags:
         - ONE
         - TWO
+        - THREE
diff --git a/testdata/extends/snapshop-config.yaml b/testdata/extends/snapshop-config.yaml
index da64fe9..8282ad3 100644
--- a/testdata/extends/snapshop-config.yaml
+++ b/testdata/extends/snapshop-config.yaml
@@ -14,6 +14,9 @@ squadron:
         image:
           repository: nginx
           tag: latest
+        null_obj: null
+        null_tags: null
         tags:
         - ONE
         - TWO
+        - THREE
diff --git a/testdata/extends/squadron.base.yaml b/testdata/extends/squadron.base.yaml
index 506492c..56ef48c 100644
--- a/testdata/extends/squadron.base.yaml
+++ b/testdata/extends/squadron.base.yaml
@@ -5,4 +5,10 @@ env:
   ONE: unknown
   THREE: baz
 tags:
-  - unknown
+  - ONE
+  - TWO
+null_tags:
+  - TWO
+null_obj:
+  ONE: unknown
+  THREE: baz
diff --git a/testdata/extends/squadron.yaml b/testdata/extends/squadron.yaml
index aee7f8a..56c66f4 100644
--- a/testdata/extends/squadron.yaml
+++ b/testdata/extends/squadron.yaml
@@ -12,5 +12,6 @@ squadron:
           ONE: foo
           TWO: bar
         tags:
-          - ONE
-          - TWO
+          - THREE
+        null_obj: ~
+        null_tags: ~