1 files changed, 8 insertions, 8 deletions
diff --git a/spec/ruby/core/encoding/converter/last_error_spec.rb b/spec/ruby/core/encoding/converter/last_error_spec.rb
index 68567737b7..78779be70b 100644
--- a/spec/ruby/core/encoding/converter/last_error_spec.rb
+++ b/spec/ruby/core/encoding/converter/last_error_spec.rb
@@ -9,45 +9,45 @@ describe "Encoding::Converter#last_error" do
 
   it "returns nil when the last conversion did not produce an error" do
     ec = Encoding::Converter.new('ascii','utf-8')
-    ec.convert('a'.force_encoding('ascii'))
+    ec.convert('a'.dup.force_encoding('ascii'))
     ec.last_error.should be_nil
   end
 
   it "returns nil when #primitive_convert last returned :destination_buffer_full" do
     ec = Encoding::Converter.new("utf-8", "iso-2022-jp")
-    ec.primitive_convert("\u{9999}", "", 0, 0, partial_input: false) \
+    ec.primitive_convert(+"\u{9999}", +"", 0, 0, partial_input: false) \
       .should == :destination_buffer_full
     ec.last_error.should be_nil
   end
 
   it "returns nil when #primitive_convert last returned :finished" do
     ec = Encoding::Converter.new("utf-8", "iso-8859-1")
-    ec.primitive_convert("glark".force_encoding('utf-8'),"").should == :finished
+    ec.primitive_convert("glark".dup.force_encoding('utf-8'), +"").should == :finished
     ec.last_error.should be_nil
   end
 
   it "returns nil if the last conversion succeeded but the penultimate failed" do
     ec = Encoding::Converter.new("utf-8", "iso-8859-1")
-    ec.primitive_convert("\xf1abcd","").should == :invalid_byte_sequence
-    ec.primitive_convert("glark".force_encoding('utf-8'),"").should == :finished
+    ec.primitive_convert(+"\xf1abcd", +"").should == :invalid_byte_sequence
+    ec.primitive_convert("glark".dup.force_encoding('utf-8'), +"").should == :finished
     ec.last_error.should be_nil
   end
 
   it "returns an Encoding::InvalidByteSequenceError when #primitive_convert last returned :invalid_byte_sequence" do
     ec = Encoding::Converter.new("utf-8", "iso-8859-1")
-    ec.primitive_convert("\xf1abcd","").should == :invalid_byte_sequence
+    ec.primitive_convert(+"\xf1abcd", +"").should == :invalid_byte_sequence
     ec.last_error.should be_an_instance_of(Encoding::InvalidByteSequenceError)
   end
 
   it "returns an Encoding::UndefinedConversionError when #primitive_convert last returned :undefined_conversion" do
     ec = Encoding::Converter.new("utf-8", "iso-8859-1")
-    ec.primitive_convert("\u{9876}","").should == :undefined_conversion
+    ec.primitive_convert(+"\u{9876}", +"").should == :undefined_conversion
     ec.last_error.should be_an_instance_of(Encoding::UndefinedConversionError)
   end
 
   it "returns an Encoding::InvalidByteSequenceError when #primitive_convert last returned :incomplete_input" do
     ec = Encoding::Converter.new("EUC-JP", "ISO-8859-1")
-    ec.primitive_convert("\xa4", "", nil, 10).should == :incomplete_input
+    ec.primitive_convert(+"\xa4", +"", nil, 10).should == :incomplete_input
     ec.last_error.should be_an_instance_of(Encoding::InvalidByteSequenceError)
   end