diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 5b6aaa5dabf..f739a7d0a0b 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -12914,7 +12914,7 @@ namespace ts {
                 const discriminantType = getUnionType(clauseTypes);
                 const caseType =
                     discriminantType.flags & TypeFlags.Never ? neverType :
-                        replacePrimitivesWithLiterals(filterType(type, t => isTypeComparableTo(discriminantType, t)), discriminantType);
+                        replacePrimitivesWithLiterals(filterType(type, t => areTypesComparable(discriminantType, t)), discriminantType);
                 if (!hasDefaultClause) {
                     return caseType;
                 }