diff --git a/cmd/efsn/config.go b/cmd/efsn/config.go
index 9d2a5678..b14f63af 100644
--- a/cmd/efsn/config.go
+++ b/cmd/efsn/config.go
@@ -30,7 +30,6 @@ import (
 	"github.com/FusionFoundation/efsn/cmd/utils"
 	"github.com/FusionFoundation/efsn/dashboard"
 	"github.com/FusionFoundation/efsn/eth"
-	"github.com/FusionFoundation/efsn/eth/downloader"
 	"github.com/FusionFoundation/efsn/node"
 	"github.com/FusionFoundation/efsn/params"
 	whisper "github.com/FusionFoundation/efsn/whisper/whisperv6"
@@ -138,11 +137,6 @@ func makeConfigNode(ctx *cli.Context) (*node.Node, gethConfig) {
 	utils.SetShhConfig(ctx, stack, &cfg.Shh)
 	utils.SetDashboardConfig(ctx, &cfg.Dashboard)
 
-	// Disable fast sync mode
-	if cfg.Eth.SyncMode == downloader.FastSync {
-		cfg.Eth.SyncMode = downloader.FullSync
-	}
-
 	// set to archival mode by default
 	// necessary to get ticket state back
 	cfg.Eth.NoPruning = true
diff --git a/cmd/utils/flags.go b/cmd/utils/flags.go
index 1b6f978f..243f5691 100644
--- a/cmd/utils/flags.go
+++ b/cmd/utils/flags.go
@@ -1138,6 +1138,10 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *eth.Config) {
 
 	if ctx.GlobalIsSet(SyncModeFlag.Name) {
 		cfg.SyncMode = *GlobalTextMarshaler(ctx, SyncModeFlag.Name).(*downloader.SyncMode)
+		if cfg.SyncMode == downloader.FastSync && downloader.FastSyncSupported() == false {
+			log.Warn("SetEthConfig: 'fast' sync mode is not supported, change to 'full' sync mode.")
+			cfg.SyncMode = downloader.FullSync
+		}
 	}
 	if ctx.GlobalIsSet(LightServFlag.Name) {
 		cfg.LightServ = ctx.GlobalInt(LightServFlag.Name)
@@ -1251,6 +1255,7 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *eth.Config) {
 	if gen := ctx.GlobalInt(TrieCacheGenFlag.Name); gen > 0 {
 		state.MaxTrieCacheGen = uint16(gen)
 	}
+	log.Info("SetEthConfig finished", "NetworkId", cfg.NetworkId, "SyncMode", cfg.SyncMode, "NoPruning", cfg.NoPruning)
 }
 
 // SetDashboardConfig applies dashboard related command line flags to the config.
diff --git a/eth/config.go b/eth/config.go
index edf4971c..561ff7de 100644
--- a/eth/config.go
+++ b/eth/config.go
@@ -35,7 +35,7 @@ import (
 
 // DefaultConfig contains default settings for use on the Ethereum main net.
 var DefaultConfig = Config{
-	SyncMode: downloader.FastSync,
+	SyncMode: downloader.DefaultSyncMode(),
 	Ethash: ethash.Config{
 		CacheDir:       "ethash",
 		CachesInMem:    2,
diff --git a/eth/downloader/modes.go b/eth/downloader/modes.go
index 8ecdf91f..fe4b9a8b 100644
--- a/eth/downloader/modes.go
+++ b/eth/downloader/modes.go
@@ -27,6 +27,17 @@ const (
 	LightSync                 // Download only the headers and terminate afterwards
 )
 
+func FastSyncSupported() bool {
+	return false
+}
+
+func DefaultSyncMode() SyncMode {
+	if FastSyncSupported() {
+		return FastSync
+	}
+	return FullSync
+}
+
 func (mode SyncMode) IsValid() bool {
 	return mode >= FullSync && mode <= LightSync
 }
diff --git a/eth/sync.go b/eth/sync.go
index ddb4cc09..035a60f4 100644
--- a/eth/sync.go
+++ b/eth/sync.go
@@ -176,23 +176,25 @@ func (pm *ProtocolManager) synchronise(peer *peer) {
 	}
 	// Otherwise try to sync with the downloader
 	mode := downloader.FullSync
-	if atomic.LoadUint32(&pm.fastSync) == 1 {
-		// Fast sync was explicitly requested, and explicitly granted
-		mode = downloader.FastSync
-	} else if currentBlock.NumberU64() == 0 && pm.blockchain.CurrentFastBlock().NumberU64() > 0 {
-		// The database seems empty as the current block is the genesis. Yet the fast
-		// block is ahead, so fast sync was enabled for this node at a certain point.
-		// The only scenario where this can happen is if the user manually (or via a
-		// bad block) rolled back a fast sync node below the sync point. In this case
-		// however it's safe to reenable fast sync.
-		atomic.StoreUint32(&pm.fastSync, 1)
-		mode = downloader.FastSync
-	}
+	if downloader.FastSyncSupported() {
+		if atomic.LoadUint32(&pm.fastSync) == 1 {
+			// Fast sync was explicitly requested, and explicitly granted
+			mode = downloader.FastSync
+		} else if currentBlock.NumberU64() == 0 && pm.blockchain.CurrentFastBlock().NumberU64() > 0 {
+			// The database seems empty as the current block is the genesis. Yet the fast
+			// block is ahead, so fast sync was enabled for this node at a certain point.
+			// The only scenario where this can happen is if the user manually (or via a
+			// bad block) rolled back a fast sync node below the sync point. In this case
+			// however it's safe to reenable fast sync.
+			atomic.StoreUint32(&pm.fastSync, 1)
+			mode = downloader.FastSync
+		}
 
-	if mode == downloader.FastSync {
-		// Make sure the peer's total difficulty we are synchronizing is higher.
-		if pm.blockchain.GetTdByHash(pm.blockchain.CurrentFastBlock().Hash()).Cmp(pTd) >= 0 {
-			return
+		if mode == downloader.FastSync {
+			// Make sure the peer's total difficulty we are synchronizing is higher.
+			if pm.blockchain.GetTdByHash(pm.blockchain.CurrentFastBlock().Hash()).Cmp(pTd) >= 0 {
+				return
+			}
 		}
 	}