diff --git a/compiler/can/src/annotation.rs b/compiler/can/src/annotation.rs
index 09395d3e3f..72f2f89f8f 100644
--- a/compiler/can/src/annotation.rs
+++ b/compiler/can/src/annotation.rs
@@ -32,6 +32,20 @@ impl<'a> NamedOrAbleVariable<'a> {
             NamedOrAbleVariable::Able(av) => av.first_seen,
         }
     }
+
+    pub fn name(&self) -> &Lowercase {
+        match self {
+            NamedOrAbleVariable::Named(nv) => &nv.name,
+            NamedOrAbleVariable::Able(av) => &av.name,
+        }
+    }
+
+    pub fn variable(&self) -> Variable {
+        match self {
+            NamedOrAbleVariable::Named(nv) => nv.variable,
+            NamedOrAbleVariable::Able(av) => av.variable,
+        }
+    }
 }
 
 /// A named type variable, not bound to an ability.
@@ -148,19 +162,13 @@ impl IntroducedVariables {
             .map(|(_, var)| var)
     }
 
+    pub fn iter_named(&self) -> impl Iterator<Item = NamedOrAbleVariable> {
+        (self.named.iter().map(NamedOrAbleVariable::Named))
+            .chain(self.able.iter().map(NamedOrAbleVariable::Able))
+    }
+
     pub fn named_var_by_name(&self, name: &Lowercase) -> Option<NamedOrAbleVariable> {
-        if let Some(nav) = self
-            .named
-            .iter()
-            .find(|nv| &nv.name == name)
-            .map(NamedOrAbleVariable::Named)
-        {
-            return Some(nav);
-        }
-        self.able
-            .iter()
-            .find(|av| &av.name == name)
-            .map(NamedOrAbleVariable::Able)
+        self.iter_named().find(|v| v.name() == name)
     }
 
     pub fn collect_able(&self) -> Vec<Variable> {
diff --git a/compiler/constrain/src/expr.rs b/compiler/constrain/src/expr.rs
index c9b41c1da8..1b820bf762 100644
--- a/compiler/constrain/src/expr.rs
+++ b/compiler/constrain/src/expr.rs
@@ -1684,18 +1684,18 @@ fn instantiate_rigids(
     let mut new_rigid_variables: Vec<Variable> = Vec::new();
 
     let mut rigid_substitution: MutMap<Variable, Variable> = MutMap::default();
-    for named in introduced_vars.named.iter() {
+    for named in introduced_vars.iter_named() {
         use std::collections::hash_map::Entry::*;
 
-        match ftv.entry(named.name.clone()) {
+        match ftv.entry(named.name().clone()) {
             Occupied(occupied) => {
                 let existing_rigid = occupied.get();
-                rigid_substitution.insert(named.variable, *existing_rigid);
+                rigid_substitution.insert(named.variable(), *existing_rigid);
             }
             Vacant(vacant) => {
                 // It's possible to use this rigid in nested defs
-                vacant.insert(named.variable);
-                new_rigid_variables.push(named.variable);
+                vacant.insert(named.variable());
+                new_rigid_variables.push(named.variable());
             }
         }
     }
diff --git a/compiler/mono/src/ir.rs b/compiler/mono/src/ir.rs
index 5bb784d3c4..099f5f8dfc 100644
--- a/compiler/mono/src/ir.rs
+++ b/compiler/mono/src/ir.rs
@@ -4750,6 +4750,7 @@ fn get_specialization<'a>(
     symbol: Symbol,
 ) -> Option<Symbol> {
     use roc_solve::ability::type_implementing_member;
+    use roc_solve::solve::instantiate_rigids;
     use roc_unify::unify::unify;
 
     match env.abilities_store.member_def(symbol) {
@@ -4759,6 +4760,7 @@ fn get_specialization<'a>(
         }
         Some(member) => {
             let snapshot = env.subs.snapshot();
+            instantiate_rigids(env.subs, member.signature_var);
             let (_, must_implement_ability) = unify(
                 env.subs,
                 symbol_var,
diff --git a/compiler/test_gen/src/gen_abilities.rs b/compiler/test_gen/src/gen_abilities.rs
index 384ba85b36..0fa3f804ab 100644
--- a/compiler/test_gen/src/gen_abilities.rs
+++ b/compiler/test_gen/src/gen_abilities.rs
@@ -88,6 +88,31 @@ fn alias_member_specialization() {
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
 fn ability_constrained_in_non_member_usage() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+            app "test" provides [ result ] to "./platform"
+
+            Hash has
+                hash : a -> U64 | a has Hash
+
+            mulHashes : a, a -> U64 | a has Hash
+            mulHashes = \x, y -> hash x * hash y
+
+            Id := U64
+            hash = \$Id n -> n
+
+            result = mulHashes ($Id 5) ($Id 7)
+            "#
+        ),
+        35,
+        u64
+    )
+}
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+fn ability_constrained_in_non_member_usage_inferred() {
     assert_evals_to!(
         indoc!(
             r#"
@@ -112,6 +137,34 @@ fn ability_constrained_in_non_member_usage() {
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
 fn ability_constrained_in_non_member_multiple_specializations() {
+    assert_evals_to!(
+        indoc!(
+            r#"
+                app "test" provides [ result ] to "./platform"
+
+                Hash has
+                    hash : a -> U64 | a has Hash
+
+                mulHashes : a, b -> U64 | a has Hash, b has Hash
+                mulHashes = \x, y -> hash x * hash y
+
+                Id := U64
+                hash = \$Id n -> n
+
+                Three := {}
+                hash = \$Three _ -> 3
+
+                result = mulHashes ($Id 100) ($Three {})
+                "#
+        ),
+        300,
+        u64
+    )
+}
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+fn ability_constrained_in_non_member_multiple_specializations_inferred() {
     assert_evals_to!(
         indoc!(
             r#"