diff --git a/src/main/java/org/embeddedt/modernfix/common/mixin/perf/optimize_surface_rules/SurfaceSystemMixin.java b/src/main/java/org/embeddedt/modernfix/common/mixin/perf/optimize_surface_rules/SurfaceSystemMixin.java
index 9c48fe9a..9a3a8e64 100644
--- a/src/main/java/org/embeddedt/modernfix/common/mixin/perf/optimize_surface_rules/SurfaceSystemMixin.java
+++ b/src/main/java/org/embeddedt/modernfix/common/mixin/perf/optimize_surface_rules/SurfaceSystemMixin.java
@@ -37,11 +37,18 @@ public class SurfaceSystemMixin {
                                                               @Local(ordinal = 0, argsOnly = true) BiomeManager manager,
                                                               @Local(ordinal = 0, argsOnly = true) ChunkAccess chunk,
                                                               @Share("chunkBiomeLookup") LocalRef<ChunkBiomeLookup> lookupRef) {
-        var lookup = MFIX_LOOKUP_CACHE.get();
-        BiomeManagerAccessor accessor = (BiomeManagerAccessor)manager;
-        lookup.prepare(accessor.mfix$getBiomeSource(), accessor.mfix$getZoomSeed(), chunk, manager);
-        lookupRef.set(lookup);
-        return lookup;
+        // If mods use their own BiomeManager subclass, we cannot trust them to use the same blurring as vanilla,
+        // so we cannot apply our optimized path
+        if (manager.getClass() == BiomeManager.class) {
+            var lookup = MFIX_LOOKUP_CACHE.get();
+            BiomeManagerAccessor accessor = (BiomeManagerAccessor)manager;
+            lookup.prepare(accessor.mfix$getBiomeSource(), accessor.mfix$getZoomSeed(), chunk, manager);
+            lookupRef.set(lookup);
+            return lookup;
+        } else {
+            lookupRef.set(null);
+            return biomeGetter;
+        }
     }
 
     @Inject(method = "buildSurface", at = @At(value = "INVOKE", target = "Lnet/minecraft/world/level/levelgen/SurfaceRules$RuleSource;apply(Ljava/lang/Object;)Ljava/lang/Object;", ordinal = 0))
@@ -60,7 +67,12 @@ public class SurfaceSystemMixin {
 
     @Redirect(method = "buildSurface", at = @At(value = "INVOKE", target = "Lnet/minecraft/world/level/biome/BiomeManager;getBiome(Lnet/minecraft/core/BlockPos;)Lnet/minecraft/core/Holder;"))
     private Holder<Biome> useFasterLookup(BiomeManager instance, BlockPos pos, @Share("chunkBiomeLookup") LocalRef<ChunkBiomeLookup> lookupRef) {
-        return lookupRef.get().apply(pos);
+        var lookup = lookupRef.get();
+        if (lookup != null) {
+            return lookup.apply(pos);
+        } else {
+            return instance.getBiome(pos);
+        }
     }
 
     @Inject(method = "buildSurface", at = @At(value = "INVOKE", target = "Lnet/minecraft/world/level/levelgen/SurfaceRules$Context;<init>(Lnet/minecraft/world/level/levelgen/SurfaceSystem;Lnet/minecraft/world/level/levelgen/RandomState;Lnet/minecraft/world/level/chunk/ChunkAccess;Lnet/minecraft/world/level/levelgen/NoiseChunk;Ljava/util/function/Function;Lnet/minecraft/core/Registry;Lnet/minecraft/world/level/levelgen/WorldGenerationContext;)V"))
diff --git a/src/main/java/org/embeddedt/modernfix/world/gen/ChunkBiomeLookup.java b/src/main/java/org/embeddedt/modernfix/world/gen/ChunkBiomeLookup.java
index 03c9b6bb..f96b4309 100644
--- a/src/main/java/org/embeddedt/modernfix/world/gen/ChunkBiomeLookup.java
+++ b/src/main/java/org/embeddedt/modernfix/world/gen/ChunkBiomeLookup.java
@@ -97,6 +97,9 @@ public class ChunkBiomeLookup implements Function<BlockPos, Holder<Biome>> {
     }
 
     public void dispose() {
+        if (this.fallbackManager == null) {
+            return;
+        }
         // Make sure we do not retain strong references to the biome holders
         Arrays.fill(biomes, null);
         this.fallbackManager = null;