diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index d5644d49e1ea4..e4f033efb58e3 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -285,7 +285,12 @@ impl<'a> CompilerCalls<'a> for RustcDefaultCalls {
                       -> Compilation {
         match matches.opt_str("explain") {
             Some(ref code) => {
-                match descriptions.find_description(&code[..]) {
+                let normalised = if !code.starts_with("E") {
+                    format!("E{0:0>4}", code)
+                } else {
+                    code.to_string()
+                };
+                match descriptions.find_description(&normalised) {
                     Some(ref description) => {
                         // Slice off the leading newline and print.
                         print!("{}", &description[1..]);