diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index d43983d4a648213b6d985a285029c50557cfecd8..6a2b855435f47a6f3152ef155b36c38dac12ac33 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -1126,9 +1126,11 @@ int mmc_hwpart_config(struct mmc *mmc,
 
 		ext_csd[EXT_CSD_ERASE_GROUP_DEF] = 1;
 
+#if CONFIG_IS_ENABLED(MMC_WRITE)
 		/* update erase group size to be high-capacity */
 		mmc->erase_grp_size =
 			ext_csd[EXT_CSD_HC_ERASE_GRP_SIZE] * 1024;
+#endif
 
 	}