diff --git a/install.ps1 b/install.ps1
index 3e0fa3b13..cf7abb20c 100644
--- a/install.ps1
+++ b/install.ps1
@@ -16,7 +16,7 @@
     # and Invoke-WebRequest throws on a cut transfer before the hash is read:
     # the site's build rewrites this line there (scripts/sitebootstrap.py).
     $mismatchAdvice = "The download was most likely cut short: try again. Within minutes of an update of this project the two files can come from caches of different ages. Waiting five minutes settles that."
-    $defaultInstallSha256 = "02b1a66c6f9d63122c8064005ec6ae7c7504820c28e5027a5894aef209be7aa5"
+    $defaultInstallSha256 = "57b285ce8de68f8ece0d1adb9f3b7a7fc8cda5ab7004c3601d5ef357353ab69e"
     $maximumInstallerBytes = 2MB
     $installerExit = 0
     $installer = if ($PSScriptRoot) { Join-Path $PSScriptRoot "install.py" } else { $null }
diff --git a/install.py b/install.py
index a1956f4d5..89a945fab 100644
--- a/install.py
+++ b/install.py
@@ -12168,16 +12168,35 @@ def _copy_reason(entry: dict, copy: LocalCopy, bios_path: Path, known: set[str])
     return _place_reason(entry, copy.path, copy.index, expected, known)[0]
 
 
+def _twin_in_place(entry: dict, files: list[dict], bios_path: Path) -> bool:
+    """Whether the name a case variant shares with another entry, but for
+    the case (bios.col and BIOS.col), is in place."""
+    folded = str(entry.get("dest", "")).casefold()
+    for twin in files:
+        if twin is entry or twin.get("case_variant") or \
+                str(twin.get("dest", "")).casefold() != folded:
+            continue
+        try:
+            if _is_file(_entry_path(bios_path, twin)):
+                return True
+        except ValueError:
+            continue
+    return False
+
+
 def _found_elsewhere(
     entry: dict, index: FolderIndex, bios_path: Path, files: list[dict],
     known: set[str], zipped: _ZippedLookup | None = None,
 ) -> tuple[str, str]:
     """(reason, folder too deep) for an entry missing at its place."""
     dest = str(entry.get("dest", ""))
-    if entry.get("case_variant"):
+    if entry.get("case_variant") and _twin_in_place(entry, files, bios_path):
         # A pack is read on Windows and macOS too, where two names that
         # differ only by case are one file: it carries one of the pair. Moving
         # the other copy here would take it from the core that opens it.
+        # Only its twin in place says a pack was used: on an empty folder the
+        # note named a pack never downloaded and pushed the BIOS files the
+        # user looked for into "... and N more".
         return ("a second name the pack leaves out: Windows and macOS see it "
                 "as the same file. Run the command without --check to add it"), ""
     name = dest.rsplit("/", 1)[-1]
diff --git a/install.sh b/install.sh
index 83346b4a8..5e88c6d10 100755
--- a/install.sh
+++ b/install.sh
@@ -23,7 +23,7 @@ DEFAULT_INSTALL_URL="https://raw.githubusercontent.com/Abdess/retrobios/main/ins
 # curl or wget stop on a cut transfer before the hash is read: the site's
 # build rewrites this line there (scripts/sitebootstrap.py).
 MISMATCH_ADVICE="The download was most likely cut short: try again. Within minutes of an update of this project the two files can come from caches of different ages. Waiting five minutes settles that."
-DEFAULT_INSTALL_SHA256="02b1a66c6f9d63122c8064005ec6ae7c7504820c28e5027a5894aef209be7aa5"
+DEFAULT_INSTALL_SHA256="57b285ce8de68f8ece0d1adb9f3b7a7fc8cda5ab7004c3601d5ef357353ab69e"
 MAX_INSTALLER_BYTES=2097152
 
 cleanup() {
diff --git a/install/launchers/index.json b/install/launchers/index.json
index 9bf791423..7d57d3af8 100644
--- a/install/launchers/index.json
+++ b/install/launchers/index.json
@@ -27,8 +27,8 @@
         {
           "dest": "roms/ports/retrobios/install.py",
           "repo_path": "install.py",
-          "size": 1096845,
-          "sha256": "02b1a66c6f9d63122c8064005ec6ae7c7504820c28e5027a5894aef209be7aa5",
+          "size": 1097676,
+          "sha256": "57b285ce8de68f8ece0d1adb9f3b7a7fc8cda5ab7004c3601d5ef357353ab69e",
           "executable": false
         },
         {
@@ -71,8 +71,8 @@
     "muos": {
       "archive": {
         "dest": "ARCHIVE/RetroBIOS.muxapp",
-        "size": 1150472,
-        "sha256": "b3261f3b02e6e4e14bbcba07d9f6f03b7b43e5e66bf20c770d4c68e8cb6bd277"
+        "size": 1151303,
+        "sha256": "3df4d9dd45f830736e40d80be6ff589f22c91bff93ea00570918ef53a072e826"
       },
       "members": [
         {
@@ -92,8 +92,8 @@
         {
           "name": "RetroBIOS/install.py",
           "repo_path": "install.py",
-          "size": 1096845,
-          "sha256": "02b1a66c6f9d63122c8064005ec6ae7c7504820c28e5027a5894aef209be7aa5",
+          "size": 1097676,
+          "sha256": "57b285ce8de68f8ece0d1adb9f3b7a7fc8cda5ab7004c3601d5ef357353ab69e",
           "executable": false
         },
         {
@@ -166,8 +166,8 @@
         {
           "dest": ".config/modules/retrobios/install.py",
           "repo_path": "install.py",
-          "size": 1096845,
-          "sha256": "02b1a66c6f9d63122c8064005ec6ae7c7504820c28e5027a5894aef209be7aa5",
+          "size": 1097676,
+          "sha256": "57b285ce8de68f8ece0d1adb9f3b7a7fc8cda5ab7004c3601d5ef357353ab69e",
           "executable": false
         },
         {
diff --git a/tests/test_install_offline.py b/tests/test_install_offline.py
index d066b105d..04b3ab018 100644
--- a/tests/test_install_offline.py
+++ b/tests/test_install_offline.py
@@ -179,14 +179,30 @@ class CheckNamesWhyAFileIsRefused(Scratch):
             self.skipTest("this filesystem does not keep case")
         data = json.loads(self.list.read_text())
         twin = next(f for f in data["files"] if f["dest"] == "gba_bios.bin")
-        data["case_variants"] = [{**twin, "dest": "twin/gba_bios.bin"}]
+        data["case_variants"] = [{**twin, "dest": "GBA_BIOS.BIN"}]
         self.list.write_text(json.dumps(data))
         self.complete()
         out = self.check()
-        self.assertIn("missing: twin/gba_bios.bin", out)
+        self.assertIn("missing: GBA_BIOS.BIN", out)
         self.assertIn("a second name the pack leaves out", out)
         self.assertNotIn("wrong folder: it is at gba_bios.bin", out)
 
+    def test_a_case_twin_is_plain_missing_when_no_pack_was_used(self):
+        """On an empty folder every case variant came first, uncapped, with
+        a note on a pack never downloaded: the BIOS files the user looked
+        for sat in "... and N more missing"."""
+        probe = self.root / "CaseProbe"
+        probe.write_text("x")
+        if (self.root / "caseprobe").exists():
+            self.skipTest("this filesystem does not keep case")
+        data = json.loads(self.list.read_text())
+        twin = next(f for f in data["files"] if f["dest"] == "gba_bios.bin")
+        data["case_variants"] = [{**twin, "dest": "GBA_BIOS.BIN"}]
+        self.list.write_text(json.dumps(data))
+        out = self.check()
+        self.assertIn("missing: GBA_BIOS.BIN", out)
+        self.assertNotIn("a second name the pack leaves out", out)
+
     def test_a_nested_bios_folder_is_named(self):
         for name, data in PAYLOAD.items():
             self.place(f"system/{name}", data)