diff --git a/book/src/background.md b/book/src/background.md
index 72339d0..abc65a5 100644
--- a/book/src/background.md
+++ b/book/src/background.md
@@ -2,4 +2,6 @@
 
 This section covers the background material required to understand the Halo 2 proving
 system. It is targeted at an ELI15 (Explain It Like I'm 15) level; if you think anything
-could do with additional explanation, let us know!
+could do with additional explanation, [let us know]!
+
+[let us know]: https://github.com/zcash/halo2/issues/new/choose