diff --git a/compiler/cpp/src/thrift/generate/t_delphi_generator.cc b/compiler/cpp/src/thrift/generate/t_delphi_generator.cc

index d3ad76a32..eac46a6c7 100644

--- a/compiler/cpp/src/thrift/generate/t_delphi_generator.cc

+++ b/compiler/cpp/src/thrift/generate/t_delphi_generator.cc

@@ -1062,7 +1062,7 @@ std::string t_delphi_generator::make_pascal_string_literal(std::string value) {

   }

   result << "'";

-  for (char const &c: value) {

+  for (signed char const c: value) {

     if( (c >= 0) && (c < 32)) {  // convert ctrl chars, but leave UTF-8 alone

       result << "#" << (int)c;  

     } else if (c == '\'') {