diff --git a/lib/rspec/core/notifications.rb b/lib/rspec/core/notifications.rb
index 93be6a4eb5..b88d54ade4 100644
--- a/lib/rspec/core/notifications.rb
+++ b/lib/rspec/core/notifications.rb
@@ -205,9 +205,17 @@ def fully_formatted(failure_number, colorizer=::RSpec::Core::Formatters::Console
         def encoding_of(string)
           string.encoding
         end
+
+        def encoded_string(string)
+          RSpec::Support::EncodedString.new(string, Encoding.default_external)
+        end
       else
         def encoding_of(_string)
         end
+
+        def encoded_string(string)
+          RSpec::Support::EncodedString.new(string)
+        end
       end
 
       def backtrace_formatter
@@ -225,8 +233,8 @@ def failure_lines
           begin
             lines = ["Failure/Error: #{read_failed_line.strip}"]
             lines << "#{exception_class_name}:" unless exception_class_name =~ /RSpec/
-            exception.message.to_s.split("\n").each do |line|
-              lines << "  #{line}" if exception.message
+            encoded_string(exception.message.to_s).split("\n").each do |line|
+              lines << "  #{line}"
             end
             lines
           end
diff --git a/spec/rspec/core/notifications_spec.rb b/spec/rspec/core/notifications_spec.rb
index 83428f5026..cbcf5c0ca4 100644
--- a/spec/rspec/core/notifications_spec.rb
+++ b/spec/rspec/core/notifications_spec.rb
@@ -100,5 +100,18 @@
       expect(lines[0]).to match %r{\AFailure\/Error}
       expect(lines[1]).to match %r{\A\s*Test exception\z}
     end
+
+    if String.method_defined?(:encoding)
+      it "returns failures_lines with invalid bytes replace by '?'" do
+        message_with_invalid_byte_sequence =
+          "\xEF \255 \xAD I have bad bytes".force_encoding(Encoding::UTF_8)
+        allow(exception).to receive(:message).
+          and_return(message_with_invalid_byte_sequence)
+
+        lines = notification.message_lines
+        expect(lines[0]).to match %r{\AFailure\/Error}
+        expect(lines[1].strip).to eq("? ? ? I have bad bytes")
+      end
+    end
   end
 end