diff --git a/lix/libfetchers/mercurial.cc b/lix/libfetchers/mercurial.cc
index f99191566..bd3037e3c 100644
--- a/lix/libfetchers/mercurial.cc
+++ b/lix/libfetchers/mercurial.cc
@@ -246,7 +246,7 @@ struct MercurialInputScheme : InputScheme
                 return makeResult(res->first, std::move(res->second));
         }
 
-        auto revOrRef = input.getRev() ? input.getRev()->gitRev() : *input.getRef();
+        auto revOrRef = input.getRev() ? fmt("id(%s)", input.getRev()->gitRev()) : *input.getRef();
 
         Attrs unlockedAttrs({
             {"type", "hg"},
@@ -269,7 +269,7 @@ struct MercurialInputScheme : InputScheme
            have to pull again. */
         if (!(input.getRev()
                 && pathExists(cacheDir)
-                && runProgram(hgOptions({ "log", "-R", cacheDir, "-r", input.getRev()->gitRev(), "--template", "1" })).second == "1"))
+                && runProgram(hgOptions({ "identify", "-R", cacheDir, "-r", revOrRef, "--template", "1" })).second == "1"))
         {
             Activity act(*logger, lvlTalkative, actUnknown, fmt("fetching Mercurial repository '%s'", actualUrl));
 
@@ -294,7 +294,7 @@ struct MercurialInputScheme : InputScheme
         }
 
         auto tokens = tokenizeString<std::vector<std::string>>(
-            runHg({ "log", "-R", cacheDir, "-r", revOrRef, "--template", "{node} {count(revset('::{rev}'))} {branch}" }));
+            runHg({ "identify", "-R", cacheDir, "-r", revOrRef, "--template", "{node} {count(revset('::{rev}'))} {branch}" }));
         assert(tokens.size() == 3);
 
         input.attrs.insert_or_assign("rev", Hash::parseAny(tokens[0], HashType::SHA1).gitRev());
@@ -307,7 +307,7 @@ struct MercurialInputScheme : InputScheme
         Path tmpDir = createTempDir();
         AutoDelete delTmpDir(tmpDir, true);
 
-        runHg({ "archive", "-R", cacheDir, "-r", input.getRev()->gitRev(), tmpDir });
+        runHg({ "archive", "-R", cacheDir, "-r", fmt("id(%s)", input.getRev()->gitRev()), tmpDir });
 
         deletePath(tmpDir + "/.hg_archival.txt");
 
diff --git a/tests/functional/fetchMercurial.sh b/tests/functional/fetchMercurial.sh
index 001e3ae00..42d838766 100644
--- a/tests/functional/fetchMercurial.sh
+++ b/tests/functional/fetchMercurial.sh
@@ -26,6 +26,7 @@ rev1=$(hg log --cwd $repo -r tip --template '{node}')
 echo world > $repo/hello
 hg commit --cwd $repo -m 'Bla2'
 rev2=$(hg log --cwd $repo -r tip --template '{node}')
+hg --cwd $repo bookmark aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 
 # Fetch an unclean branch.
 echo unclean > $repo/hello
@@ -45,6 +46,10 @@ path=$(nix eval --impure --raw --expr "(builtins.fetchMercurial \"file://$repo\"
 path2=$(nix eval --impure --raw --expr "(builtins.fetchMercurial { url = \"file://$repo\"; rev = \"$rev2\"; }).outPath")
 [[ $path = $path2 ]]
 
+out=$(nix eval --impure --raw --expr "builtins.fetchMercurial { url = \"file://$repo\"; rev = \"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\"; }" 2>&1) || status=$?
+[[ $status == 1 ]]
+[[ $out =~ 'hg failed with exit code' ]]
+
 # In pure eval mode, fetchMercurial with a revision should succeed.
 [[ $(nix eval --raw --expr "builtins.readFile (fetchMercurial { url = \"file://$repo\"; rev = \"$rev2\"; } + \"/hello\")") = world ]]