diff --git a/compiler/mono/src/ir.rs b/compiler/mono/src/ir.rs
index d937033115..3addb67f74 100644
--- a/compiler/mono/src/ir.rs
+++ b/compiler/mono/src/ir.rs
@@ -1351,7 +1351,7 @@ impl<'a> Expr<'a> {
             RuntimeErrorFunction(s) => alloc.text(format!("ErrorFunction {}", s)),
 
             GetTagId { structure, .. } => alloc
-                .text("GetTagId")
+                .text("GetTagId ")
                 .append(symbol_to_doc(alloc, *structure)),
         }
     }
@@ -7755,7 +7755,7 @@ fn match_on_lambda_set<'a>(
     hole: &'a Stmt<'a>,
 ) -> Stmt<'a> {
     match lambda_set.runtime_representation() {
-        Layout::Union(_) => {
+        Layout::Union(union_layout) => {
             let closure_tag_id_symbol = env.unique_symbol();
 
             let result = union_lambda_set_to_switch(
@@ -7773,11 +7773,9 @@ fn match_on_lambda_set<'a>(
             );
 
             // extract & assign the closure_tag_id_symbol
-            let expr = Expr::AccessAtIndex {
-                index: 0,
-                field_layouts: env.arena.alloc([Layout::Builtin(Builtin::Int64)]),
+            let expr = Expr::GetTagId {
                 structure: closure_data_symbol,
-                wrapped: Wrapped::MultiTagUnion,
+                union_layout,
             };
 
             Stmt::Let(
diff --git a/compiler/test_mono/generated/specialize_lowlevel.txt b/compiler/test_mono/generated/specialize_lowlevel.txt
index 8b7fd1f420..6f36920266 100644
--- a/compiler/test_mono/generated/specialize_lowlevel.txt
+++ b/compiler/test_mono/generated/specialize_lowlevel.txt
@@ -21,7 +21,7 @@ procedure Test.0 ():
     let Test.5 = 2i64;
     let Test.12 = 42i64;
     joinpoint Test.19 Test.13:
-        let Test.14 = Index 0 Test.13;
+        let Test.14 = GetTagId Test.13;
         joinpoint Test.15 Test.11:
             ret Test.11;
         in