diff --git a/runelite-mixins/src/main/java/net/runelite/mixins/VarbitMixin.java b/runelite-mixins/src/main/java/net/runelite/mixins/VarbitMixin.java
index 2ad03a58f6..23488c694e 100644
--- a/runelite-mixins/src/main/java/net/runelite/mixins/VarbitMixin.java
+++ b/runelite-mixins/src/main/java/net/runelite/mixins/VarbitMixin.java
@@ -72,6 +72,8 @@ public abstract class VarbitMixin implements RSClient
 	@Override
 	public int getVarbitValue(int[] varps, int varbitId)
 	{
+		assert client.isClientThread();
+
 		RSVarbit v = varbitCache.getIfPresent(varbitId);
 		if (v == null)
 		{