diff --git a/ets2panda/checker/ets/function.cpp b/ets2panda/checker/ets/function.cpp
index 2e40abf8317e6c289736f15c9d9f792682e9eb47..d89dd851913966afd1087118bc1f5e62974b129d 100644
--- a/ets2panda/checker/ets/function.cpp
+++ b/ets2panda/checker/ets/function.cpp
@@ -870,6 +870,7 @@ Signature *ETSChecker::FindMostSpecificSignature(const ArenaVector<Signature *>
             currentMinLength = result->Function()->Params().size();
         } else if (candidateLength >= currentLength) {
             continue;
+            // NOTE (smartin): all other cases below are unreachable code
         } else if (!isGeneric(candidate) && isGeneric(result)) {
             result = candidate;
         } else if (isGeneric(candidate) && !isGeneric(result)) {
@@ -950,6 +951,15 @@ void ETSChecker::SearchAmongMostSpecificTypes(Type *&mostSpecificType, Signature
             Relation()->SetNode(nullptr);
             return;
         }
+
+        if (idx >= prevSig->MinArgCount() && idx < sig->MinArgCount()) {
+            // NOTE (smartin): prefer non-optional parameters over optional ones
+            Relation()->Result(true);
+            mostSpecificType = sigType;
+            prevSig = sig;
+            return;
+        }
+
         if (isClassType && sigType->AsETSObjectType()->IsBoxedPrimitive() && mostSpecificType->IsETSObjectType() &&
             mostSpecificType->AsETSObjectType()->IsBoxedPrimitive()) {
             // NOTE (smartin): when a param with type int is available, make it more specific than other primitive