diff --git a/cmd/config.go b/cmd/config.go
index 8888dd4..fb5a1ef 100644
--- a/cmd/config.go
+++ b/cmd/config.go
@@ -8,12 +8,17 @@ import (
 )
 
 func assembleConfigForCommand(configBase *deployer.Config, configFromArgs deployer.Config, skipUserConfig bool) (deployer.Config, error) {
-	var config deployer.Config
-	if configBase == nil {
-		// Start with default configuration.
-		config = deployer.DefaultConfig()
-	} else {
-		config = *configBase
+	// Always start from the built-in defaults so that defaults (e.g.
+	// roxie.imageRegistry) are applied even when reusing an existing cluster
+	// manifest as the base configuration. Otherwise a manifest written by an
+	// older roxie (which predates such defaults) would leave those fields empty.
+	config := deployer.DefaultConfig()
+	if configBase != nil {
+		// Merge the provided base (e.g. an existing cluster manifest) on top of
+		// the defaults; non-empty values in the base take precedence.
+		if err := mergo.Merge(&config, configBase, mergo.WithOverride, mergo.WithoutDereference); err != nil {
+			return deployer.Config{}, fmt.Errorf("merging base config over defaults: %w", err)
+		}
 	}
 
 	// Apply user config on top (overriding defaults).
diff --git a/cmd/deploy_test.go b/cmd/deploy_test.go
index d0536c8..eb96dc7 100644
--- a/cmd/deploy_test.go
+++ b/cmd/deploy_test.go
@@ -364,6 +364,42 @@ func TestValidateImageRegistry(t *testing.T) {
 	}
 }
 
+func TestAssembleConfigForCommand(t *testing.T) {
+	// Isolate the user config lookup so it cannot pick up a real file on disk.
+	tmpDir := t.TempDir()
+	t.Setenv("XDG_CONFIG_HOME", tmpDir)
+	t.Setenv("HOME", tmpDir) // For non-Unix systems.
+
+	t.Run("applies defaults when no base config is provided", func(t *testing.T) {
+		config, err := assembleConfigForCommand(nil, deployer.Config{}, true)
+		require.NoError(t, err)
+		assert.Equal(t, constants.DefaultRegistry, config.Roxie.ImageRegistry)
+	})
+
+	t.Run("applies defaults even when base config (e.g. cluster manifest) omits them", func(t *testing.T) {
+		// Simulate a manifest stored by an older roxie that predates the
+		// imageRegistry field: ImageRegistry is empty. Defaults must still apply
+		// so an empty registry is not treated as a custom registry.
+		base := &deployer.Config{
+			Roxie: deployer.RoxieConfig{Version: "4.5.0"},
+		}
+		config, err := assembleConfigForCommand(base, deployer.Config{}, true)
+		require.NoError(t, err)
+		assert.Equal(t, constants.DefaultRegistry, config.Roxie.ImageRegistry)
+		// Values present in the base config are preserved.
+		assert.Equal(t, imagetag.MainTag("4.5.0"), config.Roxie.Version)
+	})
+
+	t.Run("base config overrides defaults", func(t *testing.T) {
+		base := &deployer.Config{
+			Roxie: deployer.RoxieConfig{ImageRegistry: "example.com/custom"},
+		}
+		config, err := assembleConfigForCommand(base, deployer.Config{}, true)
+		require.NoError(t, err)
+		assert.Equal(t, "example.com/custom", config.Roxie.ImageRegistry)
+	})
+}
+
 func TestApplyUserDefaults(t *testing.T) {
 	tests := []struct {
 		name     string