diff --git a/compile.c b/compile.c
index dcb180a..ba34746 100644
--- a/compile.c
+++ b/compile.c
@@ -47,15 +47,18 @@ static bool promote(env_t *env, CORD *code, type_t *actual, type_t *needed)
         return promote(env, code, Match(actual, PointerType)->pointed, needed);
     }
 
-    // Optional promotion:
+    // Optional and stack ref promotion:
     if (actual->tag == PointerType && needed->tag == PointerType)
         return true;
 
-    if (needed->tag == ClosureType && actual->tag == FunctionType && type_eq(actual, Match(needed, ClosureType)->fn)) {
+    if (needed->tag == ClosureType && actual->tag == FunctionType) {
         *code = CORD_all("(closure_t){", *code, ", NULL}");
         return true;
     }
 
+    if (needed->tag == ClosureType && actual->tag == ClosureType)
+        return true;
+
     if (needed->tag == FunctionType && actual->tag == FunctionType) {
         *code = CORD_all("(", compile_type(env, needed), ")", *code);
         return true;
diff --git a/types.c b/types.c
index ca0f77f..f7270a9 100644
--- a/types.c
+++ b/types.c
@@ -268,7 +268,10 @@ bool can_promote(type_t *actual, type_t *needed)
     }
 
     if (needed->tag == ClosureType && actual->tag == FunctionType)
-        return type_eq(actual, Match(needed, ClosureType)->fn);
+        return can_promote(actual, Match(needed, ClosureType)->fn);
+
+    if (needed->tag == ClosureType && actual->tag == ClosureType)
+        return can_promote(Match(actual, ClosureType)->fn, Match(needed, ClosureType)->fn);
 
     if (actual->tag == FunctionType && needed->tag == FunctionType) {
         for (arg_t *actual_arg = Match(actual, FunctionType)->args, *needed_arg = Match(needed, FunctionType)->args;