diff --git a/src/librustc/diagnostics.rs b/src/librustc/diagnostics.rs
index 287a45a21ead..1e10329bb55c 100644
--- a/src/librustc/diagnostics.rs
+++ b/src/librustc/diagnostics.rs
@@ -362,6 +362,10 @@ struct Foo1 { x: &bool }
               // ^ expected lifetime parameter
 struct Foo2<'a> { x: &'a bool } // correct
 
+impl Foo2 {}
+  // ^^^^ expected lifetime parameter
+impl<'a> Foo2<'a> {} // correct
+
 struct Bar1 { x: Foo2 }
               // ^^^^ expected lifetime parameter
 struct Bar2<'a> { x: Foo2<'a> } // correct
@@ -766,11 +770,40 @@ struct Foo {
 These can be fixed by declaring lifetime parameters:
 
 ```
-fn foo<'a>(x: &'a str) {}
-
 struct Foo<'a> {
     x: &'a str,
 }
+
+fn foo<'a>(x: &'a str) {}
+```
+
+Impl blocks declare lifetime parameters separately. You need to add lifetime
+parameters to an impl block if you're implementing a type that has a lifetime
+parameter of its own.
+For example:
+
+```compile_fail,E0261
+struct Foo<'a> {
+    x: &'a str,
+}
+
+// error,  use of undeclared lifetime name `'a`
+impl Foo<'a> {
+    fn foo<'a>(x: &'a str) {}
+}
+```
+
+This is fixed by declaring the impl block like this:
+
+```
+struct Foo<'a> {
+    x: &'a str,
+}
+
+// correct
+impl<'a> Foo<'a> {
+    fn foo(x: &'a str) {}
+}
 ```
 "##,