Mirror PR 162 from readme to rustdoc

Author: dtolnay

src/lib.rs

@@ -128,10 +128,11 @@
 //!   # ;
 //!   ```
 //!
-//! - If using the nightly channel, a backtrace is captured and printed with the
-//!   error if the underlying error type does not already provide its own. In
-//!   order to see backtraces, they must be enabled through the environment
-//!   variables described in [`std::backtrace`]:
+//! - If using the nightly channel, or stable with `features = ["backtrace"]`, a
+//!   backtrace is captured and printed with the error if the underlying error
+//!   type does not already provide its own. In order to see backtraces, they
+//!   must be enabled through the environment variables described in
+//!   [`std::backtrace`]:
 //!
 //!   - If you want panics and errors to both have backtraces, set
 //!     `RUST_BACKTRACE=1`;