diff --git a/cozo-core/src/parse/sys.rs b/cozo-core/src/parse/sys.rs
index e997fcb6..4f3ad820 100644
--- a/cozo-core/src/parse/sys.rs
+++ b/cozo-core/src/parse/sys.rs
@@ -10,7 +10,7 @@ use std::collections::BTreeMap;
 use std::sync::Arc;
 
 use itertools::Itertools;
-use miette::{ensure, miette, Diagnostic, Result};
+use miette::{ensure, miette, Diagnostic, Result, bail};
 use smartstring::{LazyCompact, SmartString};
 use thiserror::Error;
 
@@ -254,6 +254,12 @@ pub(crate) fn parse_sys(
                             _ => return Err(miette!("Invalid option: {}", opt_name.as_str())),
                         }
                     }
+                    if ef_construction == 0 {
+                        bail!("ef_construction must be set");
+                    }
+                    if max_elements == 0 {
+                        bail!("m_neighbours must be set");
+                    }
                     SysOp::CreateVectorIndex(HnswIndexConfig {
                         base_relation: SmartString::from(rel.as_str()),
                         index_name: SmartString::from(name.as_str()),
diff --git a/cozo-core/src/runtime/hnsw.rs b/cozo-core/src/runtime/hnsw.rs
index 7b12f27a..ccb29578 100644
--- a/cozo-core/src/runtime/hnsw.rs
+++ b/cozo-core/src/runtime/hnsw.rs
@@ -178,7 +178,7 @@ impl<'a> SessionTx<'a> {
                 self,
                 &[],
                 &[DataValue::from(i64::MIN)],
-                &[DataValue::from(1)],
+                &[DataValue::from(0)],
             )
             .next();
         if let Some(ep) = ep_res {
@@ -802,6 +802,8 @@ impl<'a> SessionTx<'a> {
                 .collect_vec();
             encountered_singletons |= neigbours.is_empty();
             for (neighbour_key, neighbour_idx, neighbour_subidx, _) in neigbours {
+                // REMARK: this still has some probability of disconnecting the graph.
+                // Should we accept that as a consequence of the probabilistic nature of the algorithm?
                 let mut out_key = vec![DataValue::from(layer)];
                 out_key.extend_from_slice(tuple_key);
                 out_key.push(DataValue::from(idx as i64));
diff --git a/cozo-core/src/runtime/relation.rs b/cozo-core/src/runtime/relation.rs
index ffe19c83..91a7e045 100644
--- a/cozo-core/src/runtime/relation.rs
+++ b/cozo-core/src/runtime/relation.rs
@@ -737,7 +737,7 @@ impl<'a> SessionTx<'a> {
         for prefix in ["fr", "to"] {
             for col in rel_handle.metadata.keys.iter() {
                 let mut col = col.clone();
-                col.name = SmartString::from(format!("{}_{}", prefix, config.index_name));
+                col.name = SmartString::from(format!("{}_{}", prefix, col.name));
                 idx_keys.push(col);
             }
             idx_keys.push(ColumnDef {
diff --git a/cozo-core/src/runtime/tests.rs b/cozo-core/src/runtime/tests.rs
index 6e771fe1..64e09914 100644
--- a/cozo-core/src/runtime/tests.rs
+++ b/cozo-core/src/runtime/tests.rs
@@ -849,3 +849,37 @@ fn test_vec_index() {
         println!("{} {} {}", row[0], row[1], row[2]);
     }
 }
+
+#[test]
+fn test_insertions() {
+    let db = DbInstance::new("mem", "", "").unwrap();
+    db.run_script(
+        r":create a {k => v: <F32; 100> default rand_vec(100)}",
+        Default::default(),
+    )
+    .unwrap();
+    db.run_script(r"?[k] <- [[1]] :put a {k}", Default::default())
+        .unwrap();
+    db.run_script(r"?[k, v] := *a{k, v}", Default::default())
+        .unwrap();
+    db.run_script(
+        r"::hnsw create a:i {fields: [v], dim: 100, ef: 200, m: 50}",
+        Default::default(),
+    )
+    .unwrap();
+    db.run_script(r"?[count(fr_k)] := *a:i{fr_k}", Default::default())
+        .unwrap();
+    db.run_script(r"?[k] <- [[1]] :put a {k}", Default::default())
+        .unwrap();
+    db.run_script(r"?[k] := k in int_range(1000) :put a {k}", Default::default()).unwrap();
+    let res = db
+        .run_script(
+            r"?[dist, k] := ~a:i{k | query: v, bind_distance: dist, k:10, ef: 200}, *a{k: 333, v}",
+            Default::default(),
+        )
+        .unwrap();
+    println!("results");
+    for row in res.into_json()["rows"].as_array().unwrap() {
+        println!("{} {}", row[0], row[1]);
+    }
+}