diff --git a/src/json.hpp b/src/json.hpp
index 915a60f4..81dc5f8f 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -8736,6 +8736,7 @@ basic_json_parser_66:
                     m_line_buffer.clear();
                     for (m_cursor = m_start; m_cursor != m_limit; ++m_cursor)
                     {
+                        assert(m_cursor != nullptr);
                         m_line_buffer.append(1, static_cast<const char>(*m_cursor));
                     }
                 }
diff --git a/src/json.hpp.re2c b/src/json.hpp.re2c
index 9b21c828..3b2c7500 100644
--- a/src/json.hpp.re2c
+++ b/src/json.hpp.re2c
@@ -7885,6 +7885,7 @@ class basic_json
                     m_line_buffer.clear();
                     for (m_cursor = m_start; m_cursor != m_limit; ++m_cursor)
                     {
+                        assert(m_cursor != nullptr);
                         m_line_buffer.append(1, static_cast<const char>(*m_cursor));
                     }
                 }