diff --git a/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/BackgroundScanHandler.java b/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/BackgroundScanHandler.java
index c148dd08..a2e658af 100644
--- a/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/BackgroundScanHandler.java
+++ b/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/BackgroundScanHandler.java
@@ -6,6 +6,7 @@
 package net.minecraftforge.fml.loading.moddiscovery;
 
 import com.mojang.logging.LogUtils;
+import net.minecraftforge.fml.loading.FMLConfig;
 import net.minecraftforge.fml.loading.ImmediateWindowHandler;
 import net.minecraftforge.fml.loading.LoadingModList;
 import net.minecraftforge.fml.loading.LogMarkers;
@@ -18,6 +19,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.*;
+import java.util.concurrent.atomic.AtomicInteger;
 
 public class BackgroundScanHandler
 {
@@ -41,10 +43,14 @@ private enum ScanStatus {
 
     public BackgroundScanHandler(final List<ModFile> modFiles) {
         this.modFiles = modFiles;
-        modContentScanner = Executors.newSingleThreadExecutor(r -> {
+        int maxThreads = FMLConfig.getIntConfigValue(FMLConfig.ConfigValue.MAX_THREADS);
+        // Leave 1 thread for Minecraft's own bootstrap
+        int poolSize = Math.max(1, maxThreads - 1);
+        AtomicInteger threadCount = new AtomicInteger();
+        modContentScanner = Executors.newFixedThreadPool(poolSize, r -> {
             final Thread thread = Executors.defaultThreadFactory().newThread(r);
             thread.setDaemon(true);
-            thread.setName("Background Scan Handler");
+            thread.setName("background-scan-handler-" + threadCount.getAndIncrement());
             return thread;
         });
         scannedFiles = new ArrayList<>();
@@ -72,7 +78,7 @@ public void submitForScanning(final ModFile file) {
         file.setFutureScanResult(future);
     }
 
-    private void addCompletedFile(final ModFile file, final ModFileScanData modFileScanData, final Throwable throwable) {
+    private synchronized void addCompletedFile(final ModFile file, final ModFileScanData modFileScanData, final Throwable throwable) {
         if (throwable != null) {
             status = ScanStatus.ERRORED;
             LOGGER.error(LogMarkers.SCAN,"An error occurred scanning file {}", file, throwable);
diff --git a/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModFile.java b/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModFile.java
index f95c4ded..1a8a4f42 100644
--- a/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModFile.java
+++ b/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModFile.java
@@ -57,7 +57,7 @@ public class ModFile implements IModFile {
     private final IModProvider provider;
     private       IModFileInfo modFileInfo;
     private ModFileScanData fileModFileScanData;
-    private CompletableFuture<ModFileScanData> futureScanResult;
+    private volatile CompletableFuture<ModFileScanData> futureScanResult;
     private List<CoreModFile> coreMods;
     private Path accessTransformer;
 
@@ -152,11 +152,11 @@ public ModFileScanData getScanResult() {
     }
 
     public void setScanResult(final ModFileScanData modFileScanData, final Throwable throwable) {
-        this.futureScanResult = null;
         this.fileModFileScanData = modFileScanData;
         if (throwable != null) {
             this.scanError = throwable;
         }
+        this.futureScanResult = null;
     }
 
     public void setFileProperties(Map<String, Object> fileProperties) {
diff --git a/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/Scanner.java b/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/Scanner.java
index 1114da2d..88ae4e9c 100644
--- a/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/Scanner.java
+++ b/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/Scanner.java
@@ -34,7 +34,11 @@ public ModFileScanData scan() {
         if (loaders != null) {
             loaders.forEach(loader -> {
                 LOGGER.debug(LogMarkers.SCAN, "Scanning {} with language loader {}", fileToScan.getFilePath(), loader.name());
-                loader.getFileVisitor().accept(result);
+                // Since we now scan files concurrently, but language loaders may not have been written with that in mind,
+                // synchronize on the language loader so it only scans one file at a time
+                synchronized (loader) {
+                    loader.getFileVisitor().accept(result);
+                }
             });
         }
         return result;