diff --git a/graphics/mapper/4.0/vts/functional/VtsHalGraphicsMapperV4_0TargetTest.cpp b/graphics/mapper/4.0/vts/functional/VtsHalGraphicsMapperV4_0TargetTest.cpp
index f55a6b7..61277ee 100644
--- a/graphics/mapper/4.0/vts/functional/VtsHalGraphicsMapperV4_0TargetTest.cpp
+++ b/graphics/mapper/4.0/vts/functional/VtsHalGraphicsMapperV4_0TargetTest.cpp
@@ -2001,6 +2001,11 @@
               mGralloc->set(bufferHandle, gralloc4::MetadataType_Dataspace, vec));
     ASSERT_EQ(Error::UNSUPPORTED,
               mGralloc->set(bufferHandle, gralloc4::MetadataType_BlendMode, vec));
+
+    // Keep optional metadata types below and populate the encoded metadata vec
+    // with some arbitrary different metadata because the common gralloc4::decode*()
+    // functions do not distinguish between an empty vec and bad value.
+    ASSERT_EQ(NO_ERROR, gralloc4::encodeDataspace(Dataspace::SRGB_LINEAR, &vec));
     ASSERT_EQ(Error::UNSUPPORTED,
               mGralloc->set(bufferHandle, gralloc4::MetadataType_Smpte2086, vec));
     ASSERT_EQ(Error::UNSUPPORTED,