diff --git a/lib/spack/spack/solver/asp.py b/lib/spack/spack/solver/asp.py
index b5fe43b25a0..7023d954e3d 100644
--- a/lib/spack/spack/solver/asp.py
+++ b/lib/spack/spack/solver/asp.py
@@ -3058,7 +3058,7 @@ def setup(
 
         candidate_compilers.update(compilers_from_reuse)
         self.possible_compilers = list(candidate_compilers)
-        self.possible_compilers.sort()
+        self.possible_compilers.sort()  # type: ignore[call-overload]
 
         self.gen.h1("Reusable concrete specs")
         self.define_concrete_input_specs(specs, self.pkgs)