diff --git a/pkg/action/package.go b/pkg/action/package.go
index b8ee21c68..9da63553a 100644
--- a/pkg/action/package.go
+++ b/pkg/action/package.go
@@ -51,9 +51,12 @@ type Package struct {
 	DependencyUpdate bool
 
 	// SourceDateEpoch, when non-nil, overrides all tar entry modification times
-	// in the produced chart archive. Set by callers that want reproducible builds.
-	// The environment variable SOURCE_DATE_EPOCH is the conventional way to supply
-	// this value from the CLI; reading that variable is the CLI's responsibility.
+	// in the produced chart archive, and also overwrites the "generated"
+	// timestamp in Chart.lock (if present) since that value is both the lock
+	// file's own tar entry modtime and part of its marshaled YAML content.
+	// Set by callers that want reproducible builds. The environment variable
+	// SOURCE_DATE_EPOCH is the conventional way to supply this value from the
+	// CLI; reading that variable is the CLI's responsibility.
 	SourceDateEpoch *time.Time
 
 	RepositoryConfig      string
diff --git a/pkg/chart/v2/chart.go b/pkg/chart/v2/chart.go
index adfaab15c..d24b3bded 100644
--- a/pkg/chart/v2/chart.go
+++ b/pkg/chart/v2/chart.go
@@ -110,6 +110,11 @@ func (ch *Chart) Dependencies() []*Chart { return ch.dependencies }
 // because tar headers have second-level granularity and timezone-independent
 // storage. This is used to produce reproducible archives when a build process
 // supplies a fixed timestamp (e.g. via SOURCE_DATE_EPOCH).
+//
+// If Lock is set, its Generated field is also overwritten with t. This is not
+// just a tar header change: Generated is marshaled into Chart.lock's own YAML
+// content, so this stamping is visible to anyone who reads the lock file out
+// of the produced archive.
 func (ch *Chart) StampModTimes(t time.Time) {
 	t = t.UTC().Truncate(time.Second)
 	ch.ModTime = t