diff --git a/README.md b/README.md
index cd80a697..f090d0ca 100644
--- a/README.md
+++ b/README.md
@@ -55,6 +55,18 @@ fn main() {
 }
 ```
 
+# Supported Rust Versions
+
+The `backtrace` crate is a core component of the standard library, and must
+at times keep up with the evolution of various platforms in order to serve
+the standard library's needs. This often means using recent libraries
+that provide unwinding and symbolication for various platforms.
+Thus `backtrace` is likely to use recent Rust features or depend on a library
+which itself uses them. Its minimum supported Rust version, by policy, is
+within a few versions of current stable, approximately "stable - 2".
+
+This policy takes precedence over versions written anywhere else in this repo.
+
 # License
 
 This project is licensed under either of