diff --git a/docs/ARCHITECTURE.md b/docs/ARCHITECTURE.md
index ad384d4..1eb1031 100644
--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@@ -492,7 +492,9 @@ The npm package adds the app-side tooling:
   install the updater has moved on. `/FORCE` reinstalls the same version (repair), `/NORUN` does
   not open the app, `/UPDATE` is the updater's path and always installs. An app renamed after its
   first release keeps its registry keys by defining `WAYBETTER_LEGACY_NAME` in its installer hooks
-  (`bundle.windows.nsis.installerHooks`).
+  (`bundle.windows.nsis.installerHooks`). An install made under the old name (its `DisplayName` is
+  still that name) counts as older than any setup of the renamed app, whatever its version number:
+  the renamed app may start its numbering again and still upgrades such an install in place.
 
 ## Consuming it
 
diff --git a/packages/waybetter/windows/installer.nsi b/packages/waybetter/windows/installer.nsi
index 8330de1..86df64c 100644
--- a/packages/waybetter/windows/installer.nsi
+++ b/packages/waybetter/windows/installer.nsi
@@ -7,7 +7,9 @@
 ;   - the same or a newer version is installed: installs nothing, opens the installed app (its
 ;     single-instance guard shows the running window) and exits 0. So an old setup left in
 ;     Downloads can never replace, restart or downgrade an install the updater has moved on;
-;   - an older version is installed: upgrades in place (app data untouched), then opens the app.
+;   - an older version is installed: upgrades in place (app data untouched), then opens the app;
+;   - an install made under the app's old name (see WAYBETTER_LEGACY_NAME below) counts as older,
+;     whatever its version number says: it is upgraded in place, data kept.
 ; Flags: `/NORUN` never opens the app, `/FORCE` reinstalls the same version (repair; it still never
 ; downgrades), `/UPDATE` is the updater's path (tauri-plugin-updater: `/UPDATE /R /ARGS ...`),
 ; which always installs and is otherwise Tauri's. `/NS` (no shortcuts) and `/D=<folder>` as in Tauri.
@@ -17,6 +19,9 @@
 ; (`bundle.windows.nsis.installerHooks`), which are included before anything here reads it:
 ;   !define WAYBETTER_LEGACY_NAME "Old Product Name"
 ;   !define WAYBETTER_LEGACY_MANUFACTURER "Old Publisher"   ; optional, defaults to the old name
+; The renamed app may start its version numbers again (a 1.0.0 after an old 1.0.2): an install
+; whose DisplayName is still the old name was written by the old app, and every setup of the
+; renamed app is newer than it.
 Unicode true
 ManifestDPIAware true
 ; wayBetter: never show a wizard.
@@ -111,6 +116,7 @@ Var ForceMode
 Var NoShortcutMode
 Var WixMode
 Var OldMainBinaryName
+Var LegacyInstall
 
 Name "${PRODUCTNAME}"
 BrandingText "${COPYRIGHT}"
@@ -330,10 +336,24 @@ Function .onInit
   ${EndIf}
 FunctionEnd
 
+; wayBetter: $LegacyInstall = 1 when the install recorded in ${UNINSTKEY} was made by the app under
+; its old name (its DisplayName is still ${LEGACYNAME}; this template writes ${PRODUCTNAME}), else 0.
+; Such an install is older than this setup whatever its version number says.
+!macro WaybetterLegacyInstall
+  StrCpy $LegacyInstall 0
+  !ifdef LEGACYNAME
+    ReadRegStr $R6 SHCTX "${UNINSTKEY}" "DisplayName"
+    ${If} $R6 == "${LEGACYNAME}"
+      StrCpy $LegacyInstall 1
+    ${EndIf}
+  !endif
+!macroend
+
 ; wayBetter: when the app is installed in $INSTDIR at this setup's version or a newer one, open it
 ; and quit with exit code 0: nothing is copied, no running app is closed, nothing is downgraded.
 ; Returns (and the install goes ahead) when nothing is installed, when the registry names an install
-; whose exe is gone, when the installed version is older, or on /FORCE with the same version.
+; whose exe is gone, when the installed version is older, when the install was made under the app's
+; old name, or on /FORCE with the same version.
 Function OpenInstalledIfCurrent
   ; $R1 the installed exe's name, $R2 the installed version, $R3 this setup compared to it
   ReadRegStr $R1 SHCTX "${UNINSTKEY}" "MainBinaryName"
@@ -344,6 +364,12 @@ Function OpenInstalledIfCurrent
     Return
   ${EndIf}
 
+  ; Installed under the old name: older, whatever its number (upgrade in place).
+  !insertmacro WaybetterLegacyInstall
+  ${If} $LegacyInstall = 1
+    Return
+  ${EndIf}
+
   ReadRegStr $R2 SHCTX "${UNINSTKEY}" "DisplayVersion"
   ${If} $R2 == ""
     ; No version in the registry: the exe's own file version, a.b.c.d -> a.b.c
@@ -389,7 +415,10 @@ Section EarlyChecks
     ; If downgrading (wayBetter: there is no reinstall page to compare the versions, so here)
     StrCpy $R0 0
     ReadRegStr $R2 SHCTX "${UNINSTKEY}" "DisplayVersion"
+    ; (An install made under the app's old name is never a downgrade target: it is older.)
+    !insertmacro WaybetterLegacyInstall
     ${If} $R2 != ""
+    ${AndIf} $LegacyInstall <> 1
       nsis_tauri_utils::SemverCompare "${VERSION}" $R2
       Pop $R0
     ${EndIf}