diff --git a/doc/manual/source/glossary.md b/doc/manual/source/glossary.md
index 592317c12..e18324ad9 100644
--- a/doc/manual/source/glossary.md
+++ b/doc/manual/source/glossary.md
@@ -343,10 +343,6 @@
 
   See [Nix Archive](store/file-system-object/content-address.html#serial-nix-archive) for details.
 
-- [`∅`]{#gloss-empty-set}
-
-  The empty set symbol. In the context of profile history, this denotes a package is not present in a particular version of the profile.
-
 - [package]{#package}
 
   A software package; files that belong together for a particular purpose, and metadata.
diff --git a/src/nix/diff-closures.cc b/src/nix/diff-closures.cc
index 984190391..ecfc907be 100644
--- a/src/nix/diff-closures.cc
+++ b/src/nix/diff-closures.cc
@@ -49,7 +49,7 @@ GroupedPaths getClosureInfo(ref<Store> store, const StorePath & toplevel)
 
 std::string showVersions(const StringSet & versions)
 {
-    if (versions.empty()) return "∅";
+    if (versions.empty()) return "(absent)";
     StringSet versions2;
     for (auto & version : versions)
         versions2.insert(version.empty() ? "(no version)" : version);