diff --git a/nc_warnings.cmake b/nc_warnings.cmake
index 4185e50..c61aaed 100644
--- a/nc_warnings.cmake
+++ b/nc_warnings.cmake
@@ -90,6 +90,12 @@ append_compile_flag(-Wold-style-cast)
 
 append_compile_flag(-Wmissing-field-initializers)
 
+# clang 12
+append_compile_flag(-Wcast-function-type)
+append_compile_flag(-Wstring-concatenation)
+append_compile_flag(-Wtautological-unsigned-char-zero-compare)
+append_compile_flag(-Wtautological-value-range-compare)
+
 # -------------------------------------------------------------------------
 # Required extensions
 #AX_APPEND_COMPILE_FLAGS([-Wgnu-flexible-array-union-member], [], [-Werror])