diff --git a/src/main/java/de/mari_023/ae2wtlib/wut/AddTerminalEvent.java b/src/main/java/de/mari_023/ae2wtlib/wut/AddTerminalEvent.java
index e8eb0e65..335a9856 100644
--- a/src/main/java/de/mari_023/ae2wtlib/wut/AddTerminalEvent.java
+++ b/src/main/java/de/mari_023/ae2wtlib/wut/AddTerminalEvent.java
@@ -32,6 +32,10 @@ public static synchronized void run() {
         HANDLERS = null;
     }
 
+    public static synchronized boolean hasRun() {
+        return HANDLERS == null;
+    }
+
     /**
      * Creates a builder to register a new terminal.
      *
diff --git a/src/main/java/de/mari_023/ae2wtlib/wut/WTDefinitions.java b/src/main/java/de/mari_023/ae2wtlib/wut/WTDefinitions.java
index 12bc872d..a008e04c 100644
--- a/src/main/java/de/mari_023/ae2wtlib/wut/WTDefinitions.java
+++ b/src/main/java/de/mari_023/ae2wtlib/wut/WTDefinitions.java
@@ -4,6 +4,11 @@ public class WTDefinitions {
     private WTDefinitions() {
     }
 
+    static {
+        if (!AddTerminalEvent.hasRun())
+            throw new IllegalStateException("Calling WTDefinitions before terminal registration happened");
+    }
+
     public static WTDefinition CRAFTING = WTDefinition.of("crafting");
     public static WTDefinition PATTERN_ENCODING = WTDefinition.of("pattern_encoding");
     public static WTDefinition PATTERN_ACCESS = WTDefinition.of("pattern_access");