diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines
index ccaea39752..d0fc7cfe60 100644
--- a/Documentation/CodingGuidelines
+++ b/Documentation/CodingGuidelines
@@ -258,6 +258,13 @@ For C programs:
    ensure your patch is clear of all compiler warnings we care about,
    by e.g. "echo DEVELOPER=1 >>config.mak".
 
+ - When using DEVELOPER=1 mode, you may see warnings from the compiler
+   like "error: unused parameter 'foo' [-Werror=unused-parameter]",
+   which indicates that a function ignores its argument. If the unused
+   parameter can't be removed (e.g., because the function is used as a
+   callback and has to match a certain interface), you can annotate the
+   individual parameters with the UNUSED keyword, like "int foo UNUSED".
+
  - We try to support a wide range of C compilers to compile Git with,
    including old ones.  As of Git v2.35.0 Git requires C99 (we check
    "__STDC_VERSION__"). You should not use features from a newer C