diff --git a/lib/set.rb b/lib/set.rb
index caf80aa930..05eb3ffb2a 100644
--- a/lib/set.rb
+++ b/lib/set.rb
@@ -237,7 +237,7 @@ class Set
   # Returns true if the set is a superset of the given set.
   def superset?(set)
     case
-    when set.instance_of?(self.class)
+    when set.instance_of?(self.class) && @hash.respond_to?(:>=)
       @hash >= set.instance_variable_get(:@hash)
     when set.is_a?(Set)
       size >= set.size && set.all? { |o| include?(o) }
@@ -250,7 +250,7 @@ class Set
   # Returns true if the set is a proper superset of the given set.
   def proper_superset?(set)
     case
-    when set.instance_of?(self.class)
+    when set.instance_of?(self.class) && @hash.respond_to?(:>)
       @hash > set.instance_variable_get(:@hash)
     when set.is_a?(Set)
       size > set.size && set.all? { |o| include?(o) }
@@ -263,7 +263,7 @@ class Set
   # Returns true if the set is a subset of the given set.
   def subset?(set)
     case
-    when set.instance_of?(self.class)
+    when set.instance_of?(self.class) && @hash.respond_to?(:<=)
       @hash <= set.instance_variable_get(:@hash)
     when set.is_a?(Set)
       size <= set.size && all? { |o| set.include?(o) }
@@ -276,7 +276,7 @@ class Set
   # Returns true if the set is a proper subset of the given set.
   def proper_subset?(set)
     case
-    when set.instance_of?(self.class)
+    when set.instance_of?(self.class) && @hash.respond_to?(:<)
       @hash < set.instance_variable_get(:@hash)
     when set.is_a?(Set)
       size < set.size && all? { |o| set.include?(o) }