diff --git a/eco-api/src/main/java/com/willfp/eco/core/display/Display.java b/eco-api/src/main/java/com/willfp/eco/core/display/Display.java
index 6e980207..2b6230c7 100644
--- a/eco-api/src/main/java/com/willfp/eco/core/display/Display.java
+++ b/eco-api/src/main/java/com/willfp/eco/core/display/Display.java
@@ -19,6 +19,9 @@ import java.util.TreeMap;
 
 /**
  * Utility class to manage client-side item display.
+ * <p>
+ * Packet display is not done on the main thread, so make sure
+ * all your modules are thread-safe.
  */
 public final class Display {
     /**
diff --git a/eco-api/src/main/java/com/willfp/eco/core/display/DisplayModule.java b/eco-api/src/main/java/com/willfp/eco/core/display/DisplayModule.java
index d14892f3..9eb14a74 100644
--- a/eco-api/src/main/java/com/willfp/eco/core/display/DisplayModule.java
+++ b/eco-api/src/main/java/com/willfp/eco/core/display/DisplayModule.java
@@ -8,6 +8,8 @@ import org.jetbrains.annotations.Nullable;
 
 /**
  * Class for all plugin-specific client-side item display modules.
+ * <p>
+ * Display modules are called in the netty thread, so make sure they are thread-safe.
  */
 public abstract class DisplayModule {
     /**