diff --git a/nac3core/src/typecheck/type_inferencer/mod.rs b/nac3core/src/typecheck/type_inferencer/mod.rs
index db86ccdbf..b92dab678 100644
--- a/nac3core/src/typecheck/type_inferencer/mod.rs
+++ b/nac3core/src/typecheck/type_inferencer/mod.rs
@@ -1181,21 +1181,38 @@ impl<'a> Inferencer<'a> {
                         slice.location,
                     ),
                     TypeEnum::TNDArray { ty: elem_ty, num_dims } => {
-                        let num_idxs = if let TypeEnum::TTuple { ty: idx_tys } =
-                            &*self.unifier.get_ty(slice.custom.unwrap())
-                        {
-                            for idx_ty in idx_tys.iter() {
-                                self.constrain(*idx_ty, self.primitives.int32, &slice.location)?;
+                        let num_idxs = match &*self.unifier.get_ty(slice.custom.unwrap()) {
+                            TypeEnum::TTuple { ty: idx_tys } => {
+                                for idx_ty in idx_tys.iter() {
+                                    // xxx: NumPy supports a tuple of tuples for "advanced indexing"
+                                    // of multidimensional arrays (sequence index -> subset). We
+                                    // don't support this, but could give a better error message.
+                                    self.constrain(
+                                        *idx_ty,
+                                        self.primitives.int32,
+                                        &slice.location,
+                                    )?;
+                                }
+                                idx_tys.len()
+                            }
+                            TypeEnum::TList { .. } | TypeEnum::TNDArray { .. } => {
+                                return report_error(
+                                    concat!(
+                                        "ndarray index is list/array, but NumPy advanced (subset)",
+                                        "indexing is not supported yet"
+                                    ),
+                                    slice.location,
+                                );
+                            }
+                            _ => {
+                                // xxx: Could lead to suboptimal error message, as higher-dimensional indexing is not mentioned?!
+                                self.constrain(
+                                    slice.custom.unwrap(),
+                                    self.primitives.int32,
+                                    &slice.location,
+                                )?;
+                                1
                             }
-                            idx_tys.len()
-                        } else {
-                            // xxx: Could lead to suboptimal error message, as higher-dimensional indexing is not mentioned?!
-                            self.constrain(
-                                slice.custom.unwrap(),
-                                self.primitives.int32,
-                                &slice.location,
-                            )?;
-                            1
                         };
 
                         if *num_dims < num_idxs {