diff --git a/include/nlohmann/detail/exceptions.hpp b/include/nlohmann/detail/exceptions.hpp
index 77c4e02b9..6af29d659 100644
--- a/include/nlohmann/detail/exceptions.hpp
+++ b/include/nlohmann/detail/exceptions.hpp
@@ -101,7 +101,10 @@ class exception : public std::exception
                     {
                         if (&element.second == current)
                         {
-                            tokens.emplace_back(element.first.data(), element.first.size());
+                            // data() is null-terminated, so a key containing
+                            // a null byte is cut short here rather than
+                            // truncating the whole message at what()
+                            tokens.emplace_back(element.first.data());
                             break;
                         }
                     }
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 0543c68ac..84b6d1b12 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -4993,7 +4993,10 @@ class exception : public std::exception
                     {
                         if (&element.second == current)
                         {
-                            tokens.emplace_back(element.first.data(), element.first.size());
+                            // data() is null-terminated, so a key containing
+                            // a null byte is cut short here rather than
+                            // truncating the whole message at what()
+                            tokens.emplace_back(element.first.data());
                             break;
                         }
                     }