diff --git a/ui/metrics/metrics.go b/ui/metrics/metrics.go
index a282e20..6d60316 100644
--- a/ui/metrics/metrics.go
+++ b/ui/metrics/metrics.go
@@ -248,6 +248,13 @@
 	m.metrics.BuildCommand = proto.String(strings.Join(cmd, " "))
 }
 
+// AddChangedEnvironmentVariable adds the changed environment variable to
+// ChangedEnvironmentVariable field.
+func (m *Metrics) AddChangedEnvironmentVariable(ChangedEnvironmentVariable string) {
+	m.metrics.ChangedEnvironmentVariable = append(m.metrics.ChangedEnvironmentVariable,
+		ChangedEnvironmentVariable)
+}
+
 // Dump exports the collected metrics from the executed build to the file at
 // out path.
 func (m *Metrics) Dump(out string) error {