diff --git a/src/fmllauncher/java/net/minecraftforge/fml/loading/ModDirTransformerDiscoverer.java b/src/fmllauncher/java/net/minecraftforge/fml/loading/ModDirTransformerDiscoverer.java
index 7e2662f19..6080deece 100644
--- a/src/fmllauncher/java/net/minecraftforge/fml/loading/ModDirTransformerDiscoverer.java
+++ b/src/fmllauncher/java/net/minecraftforge/fml/loading/ModDirTransformerDiscoverer.java
@@ -18,6 +18,7 @@ public class ModDirTransformerDiscoverer implements ITransformerDiscoveryService
         final Path modsDir = gameDirectory.resolve(FMLPaths.MODSDIR.relative());
         List<Path> paths = new ArrayList<>();
         try {
+            Files.createDirectories(modsDir);
             Files.walk(modsDir, 1).forEach(p -> {
                 if (!Files.isRegularFile(p)) return;
                 if (!p.toString().endsWith(".jar")) return;
@@ -35,4 +36,4 @@ public class ModDirTransformerDiscoverer implements ITransformerDiscoveryService
         }
         return paths;
     }
-}
\ No newline at end of file
+}
diff --git a/src/main/java/net/minecraftforge/common/util/ReverseTagWrapper.java b/src/main/java/net/minecraftforge/common/util/ReverseTagWrapper.java
index 5ac99479f..260b8b1fc 100644
--- a/src/main/java/net/minecraftforge/common/util/ReverseTagWrapper.java
+++ b/src/main/java/net/minecraftforge/common/util/ReverseTagWrapper.java
@@ -19,6 +19,7 @@
 
 package net.minecraftforge.common.util;
 
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
 import java.util.function.IntSupplier;
@@ -47,7 +48,7 @@ public class ReverseTagWrapper<T>
     {
         if (cache == null || generation != genSupplier.getAsInt())
         {
-            this.cache = new HashSet<>(colSupplier.get().getOwningTags(target));
+            this.cache = Collections.unmodifiableSet(new HashSet<>(colSupplier.get().getOwningTags(target)));
             this.generation = genSupplier.getAsInt();
         }
         return this.cache;