diff --git a/compiler/can/src/annotation.rs b/compiler/can/src/annotation.rs
index 280dd2a510..acc0da68b6 100644
--- a/compiler/can/src/annotation.rs
+++ b/compiler/can/src/annotation.rs
@@ -454,7 +454,7 @@ fn can_annotation_help(
                     None => Type::EmptyTagUnion,
                 }
             } else {
-                let tag_types = can_tags(
+                let mut tag_types = can_tags(
                     env,
                     tags.items,
                     region,
@@ -465,6 +465,11 @@ fn can_annotation_help(
                     references,
                 );
 
+                // sort here; we later instantiate type aliases, so this type might get duplicated
+                // many times. Then, when inserting into the subs, the tags are sorted.
+                // in theory we save a lot of time by sorting once here
+                tag_types.sort_by(|a, b| a.0.cmp(&b.0));
+
                 Type::TagUnion(tag_types, Box::new(ext_type))
             }
         }
diff --git a/compiler/solve/src/solve.rs b/compiler/solve/src/solve.rs
index 68185f1551..c4a4eb98dc 100644
--- a/compiler/solve/src/solve.rs
+++ b/compiler/solve/src/solve.rs
@@ -1004,7 +1004,7 @@ fn type_to_union_tags<'a>(
         for (tag, tag_argument_types) in tags {
             let new_slice = VariableSubsSlice::reserve_into_subs(subs, tag_argument_types.len());
 
-            for (i, arg) in (new_slice.slice.start as usize..).zip(tag_argument_types) {
+            for (i, arg) in (new_slice.indices()).zip(tag_argument_types) {
                 let var = type_to_variable(subs, rank, pools, arena, arg);
                 subs.variables[i] = var;
             }