diff --git a/CODING_STYLE b/CODING_STYLE
index fab928833b0..91f09e80a87 100644
--- a/CODING_STYLE
+++ b/CODING_STYLE
@@ -147,7 +147,9 @@
 
 - Do not use types like "short". They *never* make sense. Use ints,
   longs, long longs, all in unsigned+signed fashion, and the fixed
-  size types uint32_t and so on, as well as size_t, but nothing else.
+  size types uint32_t and so on, as well as size_t, but nothing
+  else. Do not use kernel types like u32 and so on, leave that to the
+  kernel.
 
 - Public API calls (i.e. functions exported by our shared libraries)
   must be marked "_public_" and need to be prefixed with "sd_". No