diff --git a/lib/Sema/CSSolver.cpp b/lib/Sema/CSSolver.cpp
index 5d76a81c7a2ea..f7aac7f597922 100644
--- a/lib/Sema/CSSolver.cpp
+++ b/lib/Sema/CSSolver.cpp
@@ -2135,7 +2135,9 @@ void ConstraintSystem::partitionGenericOperators(ArrayRef<Constraint *> constrai
   // overload choices first.
   for (auto arg : argFnType->getParams()) {
     auto argType = arg.getPlainType();
-    if (!argType || argType->hasTypeVariable())
+    argType = getFixedTypeRecursive(argType, /*wantRValue=*/true);
+
+    if (argType->isTypeVariableOrMember())
       continue;
 
     if (conformsToKnownProtocol(DC, argType, KnownProtocolKind::AdditiveArithmetic)) {