diff --git a/cmd/utils/cmd.go b/cmd/utils/cmd.go
index 45203aa1f1..64bd5808ec 100644
--- a/cmd/utils/cmd.go
+++ b/cmd/utils/cmd.go
@@ -35,7 +35,7 @@ import (
 )
 
 const (
-	importBatchSize = 2500
+	importBatchSize = 1
 )
 
 // Fatalf formats a message to standard error and exits the program.
diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index da586b370c..f9d7247645 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -58,8 +58,9 @@ var (
 	qosTuningImpact  = 0.25 // Impact that a new tuning target has on the previous value
 
 	maxQueuedHeaders  = 32 * 1024 // [eth/62] Maximum number of headers to queue for import (DOS protection)
-	maxHeadersProcess = 2048      // Number of header download results to import at once into the chain
-	maxResultsProcess = 2048      // Number of content download results to import at once into the chain
+	// set maxHeadersProcess & maxResultsProcess to 1 so calcPastMedianTime/flux dont implode.
+	maxHeadersProcess = 1 // Number of header download results to import at once into the chain
+	maxResultsProcess = 1 // Number of content download results to import at once into the chain
 
 	fsHeaderCheckFrequency = 100        // Verification frequency of the downloaded headers during fast sync
 	fsHeaderSafetyNet      = 2048       // Number of headers to discard in case a chain violation is detected
@@ -389,6 +390,14 @@ func (d *Downloader) synchronise(id string, hash common.Hash, td *big.Int, mode
 	if d.mode == FastSync && atomic.LoadUint32(&d.fsPivotFails) >= fsCriticalTrials {
 		d.mode = FullSync
 	}
+
+	// If FastSync its safe to increase maxResultsProcess
+	if d.mode == FastSync {
+		maxResultsProcess = 2048
+	} else {
+		maxResultsProcess = 1
+	}
+
 	// Retrieve the origin peer and initiate the downloading process
 	p := d.peers.Peer(id)
 	if p == nil {