diff --git a/src/ch15-05-interior-mutability.md b/src/ch15-05-interior-mutability.md
index c730d02bf3..f43d549244 100644
--- a/src/ch15-05-interior-mutability.md
+++ b/src/ch15-05-interior-mutability.md
@@ -195,7 +195,7 @@ implement a mock object to do just that, but the borrow checker won’t allow it
 
 <span class="filename">Filename: src/lib.rs</span>
 
-```rust,does_not_compile
+```rust,ignore,does_not_compile
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -275,6 +275,41 @@ shows what that looks like:
 <span class="filename">Filename: src/lib.rs</span>
 
 ```rust
+# pub trait Messenger {
+#     fn send(&self, msg: &str);
+# }
+#
+# pub struct LimitTracker<'a, T: Messenger> {
+#     messenger: &'a T,
+#     value: usize,
+#     max: usize,
+# }
+#
+# impl<'a, T> LimitTracker<'a, T>
+#     where T: Messenger {
+#     pub fn new(messenger: &T, max: usize) -> LimitTracker<T> {
+#         LimitTracker {
+#             messenger,
+#             value: 0,
+#             max,
+#         }
+#     }
+#
+#     pub fn set_value(&mut self, value: usize) {
+#         self.value = value;
+#
+#         let percentage_of_max = self.value as f64 / self.max as f64;
+#
+#         if percentage_of_max >= 1.0 {
+#             self.messenger.send("Error: You are over your quota!");
+#         } else if percentage_of_max >= 0.9 {
+#              self.messenger.send("Urgent warning: You've used up over 90% of your quota!");
+#         } else if percentage_of_max >= 0.75 {
+#             self.messenger.send("Warning: You've used up over 75% of your quota!");
+#         }
+#     }
+# }
+#
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -306,6 +341,7 @@ mod tests {
         assert_eq!(mock_messenger.sent_messages.borrow().len(), 1);
     }
 }
+# fn main() {}
 ```
 
 <span class="caption">Listing 15-22: Using `RefCell<T>` to mutate an inner