diff --git a/cmake/ci.cmake b/cmake/ci.cmake
index 8794ed078..7f2a56de6 100644
--- a/cmake/ci.cmake
+++ b/cmake/ci.cmake
@@ -356,7 +356,7 @@ set(GCC_CXXFLAGS "-std=c++11                          \
     -Wunused-result                                   \
     -Wunused-value                                    \
     -Wunused-variable                                 \
-    -Wno-useless-cast                                    \
+    -Wuseless-cast                                    \
     -Wvarargs                                         \
     -Wvariadic-macros                                 \
     -Wvector-operation-performance                    \
diff --git a/include/nlohmann/detail/input/binary_reader.hpp b/include/nlohmann/detail/input/binary_reader.hpp
index f02a15e8f..8f55e1959 100644
--- a/include/nlohmann/detail/input/binary_reader.hpp
+++ b/include/nlohmann/detail/input/binary_reader.hpp
@@ -19,6 +19,7 @@
 #include <nlohmann/detail/input/lexer.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
 #include <nlohmann/detail/meta/is_sax.hpp>
+#include <nlohmann/detail/meta/type_traits.hpp>
 #include <nlohmann/detail/value_t.hpp>
 
 namespace nlohmann
@@ -631,7 +632,7 @@ class binary_reader
             case 0x9B: // array (eight-byte uint64_t for n follow)
             {
                 std::uint64_t len{};
-                return get_number(input_format_t::cbor, len) && get_cbor_array(static_cast<std::size_t>(len), tag_handler);
+                return get_number(input_format_t::cbor, len) && get_cbor_array(detail::conditional_static_cast<std::size_t>(len), tag_handler);
             }
 
             case 0x9F: // array (indefinite length)
@@ -685,7 +686,7 @@ class binary_reader
             case 0xBB: // map (eight-byte uint64_t for n follow)
             {
                 std::uint64_t len{};
-                return get_number(input_format_t::cbor, len) && get_cbor_object(static_cast<std::size_t>(len), tag_handler);
+                return get_number(input_format_t::cbor, len) && get_cbor_object(detail::conditional_static_cast<std::size_t>(len), tag_handler);
             }
 
             case 0xBF: // map (indefinite length)
diff --git a/include/nlohmann/detail/meta/type_traits.hpp b/include/nlohmann/detail/meta/type_traits.hpp
index 163eb01be..4ee945cc9 100644
--- a/include/nlohmann/detail/meta/type_traits.hpp
+++ b/include/nlohmann/detail/meta/type_traits.hpp
@@ -435,5 +435,19 @@ struct is_constructible_tuple : std::false_type {};
 
 template<typename T1, typename... Args>
 struct is_constructible_tuple<T1, std::tuple<Args...>> : conjunction<is_constructible<T1, Args>...> {};
+
+// to avoid useless casts (see https://github.com/nlohmann/json/issues/2893#issuecomment-889152324)
+template < typename T, typename U, std::enable_if_t < !std::is_same<T, U>::value, int > = 0 >
+T conditional_static_cast(U value)
+{
+    return static_cast<T>(value);
+}
+
+template<typename T, typename U, std::enable_if_t<std::is_same<T, U>::value, int> = 0>
+T conditional_static_cast(U value)
+{
+    return value;
+}
+
 }  // namespace detail
 }  // namespace nlohmann
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 9185ea62f..07c1e1ab4 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -3835,6 +3835,20 @@ struct is_constructible_tuple : std::false_type {};
 
 template<typename T1, typename... Args>
 struct is_constructible_tuple<T1, std::tuple<Args...>> : conjunction<is_constructible<T1, Args>...> {};
+
+// to avoid useless casts (see https://github.com/nlohmann/json/issues/2893#issuecomment-889152324)
+template < typename T, typename U, std::enable_if_t < !std::is_same<T, U>::value, int > = 0 >
+T conditional_static_cast(U value)
+{
+    return static_cast<T>(value);
+}
+
+template<typename T, typename U, std::enable_if_t<std::is_same<T, U>::value, int> = 0>
+T conditional_static_cast(U value)
+{
+    return value;
+}
+
 }  // namespace detail
 }  // namespace nlohmann
 
@@ -8240,6 +8254,8 @@ struct is_sax_static_asserts
 }  // namespace detail
 }  // namespace nlohmann
 
+// #include <nlohmann/detail/meta/type_traits.hpp>
+
 // #include <nlohmann/detail/value_t.hpp>
 
 
@@ -8853,7 +8869,7 @@ class binary_reader
             case 0x9B: // array (eight-byte uint64_t for n follow)
             {
                 std::uint64_t len{};
-                return get_number(input_format_t::cbor, len) && get_cbor_array(static_cast<std::size_t>(len), tag_handler);
+                return get_number(input_format_t::cbor, len) && get_cbor_array(detail::conditional_static_cast<std::size_t>(len), tag_handler);
             }
 
             case 0x9F: // array (indefinite length)
@@ -8907,7 +8923,7 @@ class binary_reader
             case 0xBB: // map (eight-byte uint64_t for n follow)
             {
                 std::uint64_t len{};
-                return get_number(input_format_t::cbor, len) && get_cbor_object(static_cast<std::size_t>(len), tag_handler);
+                return get_number(input_format_t::cbor, len) && get_cbor_object(detail::conditional_static_cast<std::size_t>(len), tag_handler);
             }
 
             case 0xBF: // map (indefinite length)