diff --git a/include/nlohmann/detail/output/output_adapters.hpp b/include/nlohmann/detail/output/output_adapters.hpp
index aa6217ec6..ff86a6e19 100644
--- a/include/nlohmann/detail/output/output_adapters.hpp
+++ b/include/nlohmann/detail/output/output_adapters.hpp
@@ -99,7 +99,7 @@ class output_adapter
         : oa(std::make_shared<output_stream_adapter<CharType>>(s)) {}
 
     output_adapter(StringType& s)
-        : oa(std::make_shared<output_string_adapter<CharType>>(s)) {}
+        : oa(std::make_shared<output_string_adapter<CharType, StringType>>(s)) {}
 
     operator output_adapter_t<CharType>()
     {
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index b37c21c6f..4713d4da8 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -4808,7 +4808,7 @@ class output_adapter
         : oa(std::make_shared<output_stream_adapter<CharType>>(s)) {}
 
     output_adapter(StringType& s)
-        : oa(std::make_shared<output_string_adapter<CharType>>(s)) {}
+        : oa(std::make_shared<output_string_adapter<CharType, StringType>>(s)) {}
 
     operator output_adapter_t<CharType>()
     {