diff --git a/crates/nu-engine/src/eval_ir.rs b/crates/nu-engine/src/eval_ir.rs
index 161addd641..674be96f75 100644
--- a/crates/nu-engine/src/eval_ir.rs
+++ b/crates/nu-engine/src/eval_ir.rs
@@ -436,7 +436,16 @@ fn eval_instruction<D: DebugContext>(
             let val = ctx.collect_reg(*val, *span)?;
             let record_span = record_value.span();
             let mut record = record_value.into_record()?;
-            record.insert(key.coerce_into_string()?, val);
+
+            let key = key.coerce_into_string()?;
+            if let Some(old_value) = record.insert(&key, val) {
+                return Err(ShellError::ColumnDefinedTwice {
+                    col_name: key,
+                    second_use: *span,
+                    first_use: old_value.span(),
+                });
+            }
+
             ctx.put_reg(
                 *src_dst,
                 Value::record(record, record_span).into_pipeline_data(),
diff --git a/crates/nu-protocol/src/ir/mod.rs b/crates/nu-protocol/src/ir/mod.rs
index e098b9e33e..a202c7b70c 100644
--- a/crates/nu-protocol/src/ir/mod.rs
+++ b/crates/nu-protocol/src/ir/mod.rs
@@ -150,8 +150,8 @@ pub enum Instruction {
     ListPush { src_dst: RegId, item: RegId },
     /// Spread a value onto the end of a list. Used to construct list literals.
     ListSpread { src_dst: RegId, items: RegId },
-    /// Insert a key-value pair into a record. Used to construct record literals. Any existing value
-    /// for the key is overwritten.
+    /// Insert a key-value pair into a record. Used to construct record literals. Raises an error if
+    /// the key already existed in the record.
     RecordInsert {
         src_dst: RegId,
         key: RegId,