diff --git a/compiler/rustc_data_structures/src/graph/dominators/mod.rs b/compiler/rustc_data_structures/src/graph/dominators/mod.rs
index 85b030c1a4853..53ff67f60e379 100644
--- a/compiler/rustc_data_structures/src/graph/dominators/mod.rs
+++ b/compiler/rustc_data_structures/src/graph/dominators/mod.rs
@@ -2,7 +2,7 @@
 //!
 //! Algorithm based on Loukas Georgiadis,
 //! "Linear-Time Algorithms for Dominators and Related Problems",
-//! <ftp://ftp.cs.princeton.edu/techreports/2005/737.pdf>
+//! <https://www.cs.princeton.edu/techreports/2005/737.pdf>
 //!
 //! Additionally useful is the original Lengauer-Tarjan paper on this subject,
 //! "A Fast Algorithm for Finding Dominators in a Flowgraph"