diff --git a/lib/steep/subtyping/check.rb b/lib/steep/subtyping/check.rb
index e77d3209..a99a255b 100644
--- a/lib/steep/subtyping/check.rb
+++ b/lib/steep/subtyping/check.rb
@@ -354,20 +354,19 @@ def check_type0(relation)
         when relation.super_type.is_a?(AST::Types::Var) || relation.sub_type.is_a?(AST::Types::Var)
           Failure(relation, Result::Failure::UnknownPairError.new(relation: relation))
 
-        when relation.sub_type.is_a?(AST::Types::Union)
+        when relation.super_type.is_a?(AST::Types::Intersection)
           All(relation) do |result|
-            relation.sub_type.types.each do |sub_type|
-              rel = Relation.new(sub_type: sub_type, super_type: relation.super_type)
-              result.add(rel) do
+            relation.super_type.types.each do |super_type|
+              result.add(Relation.new(sub_type: relation.sub_type, super_type: super_type)) do |rel|
                 check_type(rel)
               end
             end
           end
 
-        when relation.super_type.is_a?(AST::Types::Union)
-          Any(relation) do |result|
-            relation.super_type.types.sort_by {|ty| (path = hole_path(ty)) ? -path.size : -Float::INFINITY }.each do |super_type|
-              rel = Relation.new(sub_type: relation.sub_type, super_type: super_type)
+        when relation.sub_type.is_a?(AST::Types::Union)
+          All(relation) do |result|
+            relation.sub_type.types.each do |sub_type|
+              rel = Relation.new(sub_type: sub_type, super_type: relation.super_type)
               result.add(rel) do
                 check_type(rel)
               end
@@ -384,10 +383,11 @@ def check_type0(relation)
             end
           end
 
-        when relation.super_type.is_a?(AST::Types::Intersection)
-          All(relation) do |result|
-            relation.super_type.types.each do |super_type|
-              result.add(Relation.new(sub_type: relation.sub_type, super_type: super_type)) do |rel|
+        when relation.super_type.is_a?(AST::Types::Union)
+          Any(relation) do |result|
+            relation.super_type.types.sort_by {|ty| (path = hole_path(ty)) ? -path.size : -Float::INFINITY }.each do |super_type|
+              rel = Relation.new(sub_type: relation.sub_type, super_type: super_type)
+              result.add(rel) do
                 check_type(rel)
               end
             end