diff --git a/include/plat/common/platform.h b/include/plat/common/platform.h
index 708cbcd..faccf31 100644
--- a/include/plat/common/platform.h
+++ b/include/plat/common/platform.h
@@ -399,7 +399,7 @@
 size_t plat_rmmd_get_el3_rmm_shared_mem(uintptr_t *shared);
 int plat_rmmd_load_manifest(struct rmm_manifest *manifest);
 int plat_rmmd_mecid_key_update(uint16_t mecid);
-#endif
+#endif /* ENABLE_RME */
 
 /*******************************************************************************
  * Optional BL31 functions (may be overridden)
diff --git a/plat/arm/board/neoverse_rd/platform/rdv3/rdv3_common.c b/plat/arm/board/neoverse_rd/platform/rdv3/rdv3_common.c
index b1ee5e6..ac1f893 100644
--- a/plat/arm/board/neoverse_rd/platform/rdv3/rdv3_common.c
+++ b/plat/arm/board/neoverse_rd/platform/rdv3/rdv3_common.c
@@ -193,7 +193,8 @@
 int plat_rmmd_mecid_key_update(uint16_t mecid)
 {
 	/*
-	 * TODO
+	 * RDV3 does not support FEAT_MEC.
+	 * This empty hook is for compilation to succeed.
 	 */
 	return 0;
 }
diff --git a/services/std_svc/rmmd/rmmd_main.c b/services/std_svc/rmmd/rmmd_main.c
index e94b048..9f9894e 100644
--- a/services/std_svc/rmmd/rmmd_main.c
+++ b/services/std_svc/rmmd/rmmd_main.c
@@ -479,6 +479,14 @@
 	int ret;
 
 	/*
+	 * Check whether FEAT_MEC is supported by the hardware. If not, return
+	 * unknown SMC.
+	 */
+	if (is_feat_mec_supported() == false) {
+		return E_RMM_UNK;
+	}
+
+	/*
 	 * Check whether the mecid parameter is at most MECIDR_EL2.MECIDWidthm1 + 1
 	 * in length.
 	 */