diff --git a/src/main/java/net/minestom/server/world/biomes/BiomeManager.java b/src/main/java/net/minestom/server/world/biomes/BiomeManager.java
index a803c37a9..55904c7a5 100644
--- a/src/main/java/net/minestom/server/world/biomes/BiomeManager.java
+++ b/src/main/java/net/minestom/server/world/biomes/BiomeManager.java
@@ -28,7 +28,7 @@ public class BiomeManager {
      *
      * @param biome the biome to add
      */
-    public void addBiome(Biome biome) {
+    public synchronized void addBiome(Biome biome) {
         this.biomes.put(biome.getId(), biome);
     }
 
@@ -37,7 +37,7 @@ public class BiomeManager {
      *
      * @param biome the biome to remove
      */
-    public void removeBiome(Biome biome) {
+    public synchronized void removeBiome(Biome biome) {
         this.biomes.remove(biome.getId());
     }