diff --git a/README.md b/README.md
index df097ca9e3f..6a264034773 100644
--- a/README.md
+++ b/README.md
@@ -11,9 +11,9 @@ name                   | default | meaning
 approx_constant        | warn    | the approximate of a known float constant (in `std::f64::consts` or `std::f32::consts`) is found; suggests to use the constant
 bad_bit_mask           | deny    | expressions of the form `_ & mask == select` that will only ever return `true` or `false` (because in the example `select` containing bits that `mask` doesn't have)
 box_vec                | warn    | usage of `Box<Vec<T>>`, vector elements are already on the heap
-cast_possible_overflow | allow   | casts that may cause overflow
-cast_precision_loss    | allow   | casts that cause loss of precision
-cast_sign_loss         | allow   | casts from signed types to unsigned types
+cast_possible_overflow | allow   | casts that may cause overflow, e.g `x as u8` where `x: u32`, or `x as i32` where `x: f32`
+cast_precision_loss    | allow   | casts that cause loss of precision, e.g `x as f32` where `x: u64`
+cast_sign_loss         | allow   | casts from signed types to unsigned types, e.g `x as u32` where `x: i32`
 cmp_nan                | deny    | comparisons to NAN (which will always return false, which is probably not intended)
 cmp_owned              | warn    | creating owned instances for comparing with others, e.g. `x == "foo".to_string()`
 collapsible_if         | warn    | two nested `if`-expressions can be collapsed into one, e.g. `if x { if y { foo() } }` can be written as `if x && y { foo() }`
diff --git a/src/types.rs b/src/types.rs
index 17ebb791c3c..d6081153f01 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -140,11 +140,11 @@ impl LintPass for UnitCmp {
 pub struct CastPass;
 
 declare_lint!(pub CAST_PRECISION_LOSS, Allow,
-              "casts that cause loss of precision");
+              "casts that cause loss of precision, e.g `x as f32` where `x: u64`");
 declare_lint!(pub CAST_SIGN_LOSS, Allow,
-              "casts from signed types to unsigned types");
+              "casts from signed types to unsigned types, e.g `x as u32` where `x: i32`");
 declare_lint!(pub CAST_POSSIBLE_OVERFLOW, Allow,
-              "casts that may cause overflow");
+              "casts that may cause overflow, e.g `x as u8` where `x: u32`, or `x as i32` where `x: f32`");
 
 impl LintPass for CastPass {
     fn get_lints(&self) -> LintArray {