1 files changed, 2 insertions, 2 deletions
diff --git a/spec/ruby/core/string/rpartition_spec.rb b/spec/ruby/core/string/rpartition_spec.rb
index 21e87f530a..cef0384c73 100644
--- a/spec/ruby/core/string/rpartition_spec.rb
+++ b/spec/ruby/core/string/rpartition_spec.rb
@@ -48,7 +48,7 @@ describe "String#rpartition with String" do
   end
 
   it "handles a pattern in a superset encoding" do
-    string = "hello".force_encoding(Encoding::US_ASCII)
+    string = "hello".dup.force_encoding(Encoding::US_ASCII)
 
     result = string.rpartition("é")
 
@@ -59,7 +59,7 @@ describe "String#rpartition with String" do
   end
 
   it "handles a pattern in a subset encoding" do
-    pattern = "o".force_encoding(Encoding::US_ASCII)
+    pattern = "o".dup.force_encoding(Encoding::US_ASCII)
 
     result = "héllo world".rpartition(pattern)