diff --git a/README.md b/README.md
index 14a5e56cdea..cf3b3e1ffdd 100644
--- a/README.md
+++ b/README.md
@@ -24,6 +24,15 @@ We have a bunch of lint categories to allow you to choose how much Clippy is sup
 
 More to come, please [file an issue](https://github.com/rust-lang-nursery/rust-clippy/issues) if you have ideas!
 
+Only the following of those categories are enabled by default:
+
+* `clippy::style`
+* `clippy::correctness`
+* `clippy::complexity`
+* `clippy::perf`
+
+Other categories need to be enabled in order for their lints to be executed.
+
 Table of contents:
 
 *   [Usage instructions](#usage)
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index c343cf364f6..7cdc0f43b34 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -46,6 +46,8 @@ extern crate syntax_pos;
 
 use toml;
 
+// Currently, categories "style", "correctness", "complexity" and "perf" are enabled by default,
+// as said in the README.md of this repository. If this changes, please update README.md.
 macro_rules! declare_clippy_lint {
     { pub $name:tt, style, $description:tt } => {
         declare_tool_lint! { pub clippy::$name, Warn, $description, report_in_external_macro: true }