diff --git a/browser/installer/windows/nsis/shared.nsh b/browser/installer/windows/nsis/shared.nsh
index abb430be8919..0529ac4529db 100755
--- a/browser/installer/windows/nsis/shared.nsh
+++ b/browser/installer/windows/nsis/shared.nsh
@@ -193,12 +193,12 @@ ${If} $TmpVal == "HKCU"
                     "DidRegisterDefaultBrowserAgent"
   ${If} $0 != 0
   ${OrIf} ${Errors}
-    Exec '"$INSTDIR\default-browser-agent.exe" register-task $AppUserModelID'
+    ExecWait '"$INSTDIR\default-browser-agent.exe" register-task $AppUserModelID'
   ${EndIf}
 ${ElseIf} $TmpVal == "HKLM"
   ; If we're the privileged PostUpdate, make sure that the unprivileged one
   ; will have permission to create a task by clearing out the old one first.
-  Exec '"$INSTDIR\default-browser-agent.exe" unregister-task $AppUserModelID'
+  ExecWait '"$INSTDIR\default-browser-agent.exe" unregister-task $AppUserModelID'
 ${EndIf}
 !endif
 
diff --git a/toolkit/mozapps/update/updater/updater.cpp b/toolkit/mozapps/update/updater/updater.cpp
index 02e35ed81aa2..a04227d7b99e 100644
--- a/toolkit/mozapps/update/updater/updater.cpp
+++ b/toolkit/mozapps/update/updater/updater.cpp
@@ -1979,8 +1979,6 @@ bool LaunchWinPostProcess(const WCHAR* installationDir,
 
   WCHAR exefile[MAX_PATH + 1];
   WCHAR exearg[MAX_PATH + 1];
-  WCHAR exeasync[10];
-  bool async = true;
   if (!GetPrivateProfileStringW(L"PostUpdateWin", L"ExeRelPath", nullptr,
                                 exefile, MAX_PATH + 1, inifile)) {
     return false;
@@ -1991,12 +1989,6 @@ bool LaunchWinPostProcess(const WCHAR* installationDir,
     return false;
   }
 
-  if (!GetPrivateProfileStringW(
-          L"PostUpdateWin", L"ExeAsync", L"TRUE", exeasync,
-          sizeof(exeasync) / sizeof(exeasync[0]), inifile)) {
-    return false;
-  }
-
   // The relative path must not contain directory traversals, current directory,
   // or colons.
   if (wcsstr(exefile, L"..") != nullptr || wcsstr(exefile, L"./") != nullptr ||
@@ -2057,11 +2049,6 @@ bool LaunchWinPostProcess(const WCHAR* installationDir,
   wcsncpy(cmdline, dummyArg, len);
   wcscat(cmdline, exearg);
 
-  if (sUsingService || !_wcsnicmp(exeasync, L"false", 6) ||
-      !_wcsnicmp(exeasync, L"0", 2)) {
-    async = false;
-  }
-
   // We want to launch the post update helper app to update the Windows
   // registry even if there is a failure with removing the uninstall.update
   // file or copying the update.log file.
@@ -2080,9 +2067,7 @@ bool LaunchWinPostProcess(const WCHAR* installationDir,
                            workingDirectory, &si, &pi);
   free(cmdline);
   if (ok) {
-    if (!async) {
-      WaitForSingleObject(pi.hProcess, INFINITE);
-    }
+    WaitForSingleObject(pi.hProcess, INFINITE);
     CloseHandle(pi.hProcess);
     CloseHandle(pi.hThread);
   }
@@ -3318,26 +3303,6 @@ int NS_main(int argc, NS_tchar** argv) {
         return 0;
       }
 
-#  ifdef MOZ_MAINTENANCE_SERVICE
-      // If we started the service command, and it finished, check the secure
-      // update status file to make sure that it succeeded, and if it did we
-      // need to launch the PostUpdate process in the unelevated updater which
-      // is running in the current user's session. Note that we don't need to do
-      // this when staging an update since the PostUpdate step runs during the
-      // replace request.
-      if (useService && !sStagedUpdate) {
-        bool updateStatusSucceeded = false;
-        if (IsSecureUpdateStatusSucceeded(updateStatusSucceeded) &&
-            updateStatusSucceeded) {
-          if (!LaunchWinPostProcess(gInstallDirPath, gPatchDirPath)) {
-            fprintf(stderr,
-                    "The post update process which runs as the user"
-                    " for service update could not be launched.");
-          }
-        }
-      }
-#  endif
-
       // If we didn't want to use the service at all, or if an update was
       // already happening, or launching the service command failed, then
       // launch the elevated updater.exe as we do without the service.
@@ -3393,10 +3358,23 @@ int NS_main(int argc, NS_tchar** argv) {
         }
       }
 
-      // Note: The PostUpdate process is launched by the elevated updater which
-      // is running in the current user's session when the update is successful
-      // and doesn't need to be launched here by the unelevated updater as is
-      // done when the maintenance service launches the updater code above.
+      // If we started the elevated updater, and it finished, check the secure
+      // update status file to make sure that it succeeded, and if it did we
+      // need to launch the PostUpdate process in the unelevated updater which
+      // is running in the current user's session. Note that we don't need to do
+      // this when staging an update since the PostUpdate step runs during the
+      // replace request.
+      if (!sStagedUpdate) {
+        bool updateStatusSucceeded = false;
+        if (IsSecureUpdateStatusSucceeded(updateStatusSucceeded) &&
+            updateStatusSucceeded) {
+          if (!LaunchWinPostProcess(gInstallDirPath, gPatchDirPath)) {
+            fprintf(stderr,
+                    "The post update process which runs as the user"
+                    " for service update could not be launched.");
+          }
+        }
+      }
 
       CloseHandle(elevatedFileHandle);