1 files changed, 9 insertions, 1 deletions
diff --git a/source/slang/slang-check-overload.cpp b/source/slang/slang-check-overload.cpp
index 7a89f2e23..6c0a7f184 100644
--- a/source/slang/slang-check-overload.cpp
+++ b/source/slang/slang-check-overload.cpp
@@ -994,10 +994,18 @@ bool SemanticsVisitor::TryCheckOverloadCandidateConstraints(
         auto sup = getSup(m_astBuilder, constraintDeclRef);
 
         auto subTypeWitness = tryGetSubtypeWitness(sub, sup);
-        if (subTypeWitness)
+
+        bool witnessIsOptional = isWitnessUncheckedOptional(subTypeWitness);
+        bool constraintIsOptional = constraintDecl->hasModifier<OptionalConstraintModifier>();
+
+        if (subTypeWitness && (!witnessIsOptional || constraintIsOptional))
         {
             newArgs.add(subTypeWitness);
         }
+        else if (!subTypeWitness && constraintIsOptional)
+        {
+            newArgs.add(m_astBuilder->getOrCreate<NoneWitness>());
+        }
         else
         {
             if (context.mode != OverloadResolveContext::Mode::JustTrying)