diff --git a/kernel/lib_log.c b/kernel/lib_log.c
index 45568926..7c71addc 100644
--- a/kernel/lib_log.c
+++ b/kernel/lib_log.c
@@ -367,7 +367,7 @@ bool log_finalize(struct log_status *logst, int len, void (*endio)(void *private
 		unsigned char checksum[MARS_DIGEST_SIZE];
 
 		check_flags |=
-		  mars_digest(usable_digest_mask,
+		  mars_digest(usable_digest_mask & ~disabled_log_digests,
 			      &used_log_digest,
 			      checksum,
 			      data + logst->payload_offset, len);
diff --git a/kernel/mars_copy.c b/kernel/mars_copy.c
index 4472543e..d55c9dd7 100644
--- a/kernel/mars_copy.c
+++ b/kernel/mars_copy.c
@@ -384,7 +384,7 @@ __u32 _make_flags(bool verify_mode, bool is_local)
 	if (is_local)
 		return available_digest_mask | MREF_NODATA;
 
-	return usable_digest_mask | MREF_NODATA;
+	return (usable_digest_mask & ~disabled_net_digests) | MREF_NODATA;
 }
 
 
diff --git a/kernel/sy_old/mars_main.c b/kernel/sy_old/mars_main.c
index b93362c7..9d8aeb75 100644
--- a/kernel/sy_old/mars_main.c
+++ b/kernel/sy_old/mars_main.c
@@ -81,6 +81,9 @@
 int usable_features_version = 0;
 int usable_strategy_version = 0;
 
+__u32 disabled_log_digests = 0;
+__u32 disabled_net_digests = 0;
+
 static int _tmp_features_version = OPTIONAL_FEATURES_VERSION;
 static int _tmp_strategy_version = OPTIONAL_STRATEGY_VERSION;
 
@@ -5642,6 +5645,15 @@ int make_defaults(void *buf, struct mars_dent *dent)
 
 	if (!strcmp(dent->d_name, "sync-limit")) {
 		sscanf(dent->new_link, "%d", &global_sync_limit);
+	} else if (!strcmp(dent->d_name, "disabled-log-digests")) {
+		sscanf(dent->new_link, "0x%x", &disabled_log_digests);
+	} else if (!strcmp(dent->d_name, "disabled-net-digests")) {
+		__u32 tmp = 0;
+
+		sscanf(dent->new_link, "0x%x", &tmp);
+		/* at least one digest must remain usable */
+		tmp &= ~MREF_CHKSUM_MD5_OLD;
+		disabled_net_digests = tmp;
 	} else {
 		MARS_DBG("unimplemented default '%s'\n", dent->d_name);
 	}