diff --git a/src/entity.zig b/src/entity.zig
index d2edf20c..2d56f2a6 100644
--- a/src/entity.zig
+++ b/src/entity.zig
@@ -101,7 +101,7 @@ pub const ClientEntityManager = struct {
 	fn update() void {
 		std.debug.assert(!mutex.tryLock()); // The mutex should be locked when calling this function.
 		var time = @truncate(i16, std.time.milliTimestamp());
-		time -%= timeDifference.difference;
+		time -%= timeDifference.difference.load(.Monotonic);
 		for(entities.items) |*ent| {
 			ent.update(time, lastTime);
 		}
diff --git a/src/itemdrop.zig b/src/itemdrop.zig
index da8f01b5..2eeb27db 100644
--- a/src/itemdrop.zig
+++ b/src/itemdrop.zig
@@ -493,13 +493,19 @@ pub const ClientItemDropManager = struct {
 			vel[i][2] = @bitCast(f64, std.mem.readIntBig(u64, data[42..50]));
 			data = data[50..];
 		}
+		self.super.mutex.lock();
+		defer self.super.mutex.unlock();
 		self.interpolation.updatePosition(@ptrCast(*[maxf64Capacity]f64, &pos), @ptrCast(*[maxf64Capacity]f64, &vel), time); // TODO: Only update the ones we actually changed.
 	}
 
 	pub fn updateInterpolationData(self: *ClientItemDropManager) void {
 		var time = @truncate(i16, std.time.milliTimestamp()) -% settings.entityLookback;
-		time -%= self.timeDifference.difference;
-		self.interpolation.updateIndexed(time, self.lastTime, &self.super.indices, 4);
+		time -%= self.timeDifference.difference.load(.Monotonic);
+		{
+			self.super.mutex.lock();
+			defer self.super.mutex.unlock();
+			self.interpolation.updateIndexed(time, self.lastTime, &self.super.indices, 4);
+		}
 		self.lastTime = time;
 	}
 
@@ -731,7 +737,9 @@ pub const ItemDropRenderer = struct {
 		c.glUniform3fv(itemUniforms.ambientLight, 1, @ptrCast([*c]const f32, &ambientLight));
 		c.glUniformMatrix4fv(itemUniforms.viewMatrix, 1, c.GL_FALSE, @ptrCast([*c]const f32, &game.camera.viewMatrix));
 		c.glUniform1f(itemUniforms.sizeScale, @floatCast(f32, ItemDropManager.diameter/4.0));
-		const itemDrops = game.world.?.itemDrops.super;
+		var itemDrops = &game.world.?.itemDrops.super;
+		itemDrops.mutex.lock();
+		defer itemDrops.mutex.unlock();
 		for(itemDrops.indices[0..itemDrops.size]) |i| {
 			if(itemDrops.list.items(.itemStack)[i].item) |item| {
 				var pos = itemDrops.list.items(.pos)[i];
diff --git a/src/utils.zig b/src/utils.zig
index 1e3f9797..483f7373 100644
--- a/src/utils.zig
+++ b/src/utils.zig
@@ -591,20 +591,20 @@ pub fn GenericInterpolation(comptime elements: comptime_int) type {
 }
 
 pub const TimeDifference = struct {
-	difference: i16 = 0,
+	difference: std.atomic.Atomic(i16) = std.atomic.Atomic(i16).init(0),
 	firstValue: bool = true,
 
 	pub fn addDataPoint(self: *TimeDifference, time: i16) void {
 		const currentTime = @truncate(i16, std.time.milliTimestamp());
 		const timeDifference = currentTime -% time;
 		if(self.firstValue) {
-			self.difference = timeDifference;
+			self.difference.store(timeDifference, .Monotonic);
 			self.firstValue = false;
 		}
-		if(timeDifference -% self.difference > 0) {
-			self.difference +%= 1;
-		} else if(timeDifference -% self.difference < 0) {
-			self.difference -%= 1;
+		if(timeDifference -% self.difference.load(.Monotonic) > 0) {
+			_ = @atomicRmw(i16, &self.difference.value, .Add, 1, .Monotonic);
+		} else if(timeDifference -% self.difference.load(.Monotonic) < 0) {
+			_ = @atomicRmw(i16, &self.difference.value, .Add, -1, .Monotonic);
 		}
 	}
 };
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