diff --git a/apex/builder.go b/apex/builder.go
index e59dc96..41f1cc7 100644
--- a/apex/builder.go
+++ b/apex/builder.go
@@ -872,7 +872,7 @@
 		return a.containerCertificateFile, a.containerPrivateKeyFile
 	}
 
-	cert := String(a.properties.Certificate)
+	cert := String(a.overridableProperties.Certificate)
 	if cert == "" {
 		return ctx.Config().DefaultAppCertificate(ctx)
 	}