diff -r a55a891a4f67 -r 04ac5f2771c8 src/luan/modules/BasicLuan.java
--- a/src/luan/modules/BasicLuan.java	Thu Dec 28 11:36:24 2023 -0700
+++ b/src/luan/modules/BasicLuan.java	Sat Dec 30 18:41:35 2023 -0700
@@ -59,11 +59,17 @@
 			size = list.size();
 		}
 
-		@Override public Object[] call(Luan luan,Object[] args) {
+		@Override public Object[] call(Luan luan,Object[] args) throws LuanException {
 			if( i >= size )
 				return LuanFunction.NOTHING;
-			Object val = list.get(i++);
-			return new Object[]{i,val};
+			try {
+				Object val = list.get(i++);
+				return new Object[]{i,val};
+			} catch(IndexOutOfBoundsException e) {
+				if( size != list.size() )
+					throw new LuanException("list was modified during ipairs iteration");
+				throw e;
+			}
 		}
 
 		@Override public boolean isImmutable() {