--- a/src/Doc/Tutorial/document/basics.tex	Wed Jul 18 12:21:55 2018 +0200
+++ b/src/Doc/Tutorial/document/basics.tex	Wed Jul 18 16:44:01 2018 +0200
@@ -85,7 +85,7 @@
 \end{warn}
 HOL's theory collection is available online at
 \begin{center}\small
-    \url{http://isabelle.in.tum.de/library/HOL/}
+    \url{https://isabelle.in.tum.de/library/HOL/}
 \end{center}
 and is recommended browsing. In subdirectory \texttt{Library} you find
 a growing library of useful theories that are not part of \isa{Main}