diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 565d01bf024..b14c6be383c 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -6235,6 +6235,9 @@ namespace ts {
             if (relation === assignableRelation || relation === comparableRelation) {
                 if (source.flags & TypeFlags.Any) return true;
                 if (source.flags & (TypeFlags.Number | TypeFlags.NumberLiteral) && target.flags & TypeFlags.Enum) return true;
+                if (source.flags & (TypeFlags.Number | TypeFlags.NumberLiteral) &&
+                    target.flags & TypeFlags.Union &&
+                    forEach((target as UnionType).types, t => t.flags & TypeFlags.EnumLike)) return true;
                 if (source.flags & TypeFlags.NumberLiteral && target.flags & TypeFlags.EnumLiteral && (<LiteralType>source).text === (<LiteralType>target).text) return true;
             }
             return false;