diff --git a/include/nlohmann/detail/output/binary_writer.hpp b/include/nlohmann/detail/output/binary_writer.hpp
index 490cf63bb..0f994e89a 100644
--- a/include/nlohmann/detail/output/binary_writer.hpp
+++ b/include/nlohmann/detail/output/binary_writer.hpp
@@ -1694,7 +1694,7 @@ class binary_writer
     const bool is_little_endian = little_endianness();
 
     /// whether to write in bjdata format
-    bool is_bjdata = false;
+    const bool is_bjdata = false;
 
     /// the output
     output_adapter_t<CharType> oa = nullptr;
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 7e01ab952..92b916b3d 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -15518,7 +15518,7 @@ class binary_writer
     const bool is_little_endian = little_endianness();
 
     /// whether to write in bjdata format
-    bool is_bjdata = false;
+    const bool is_bjdata = false;
 
     /// the output
     output_adapter_t<CharType> oa = nullptr;