diff --git a/browser/app/nsBrowserApp.cpp b/browser/app/nsBrowserApp.cpp
--- a/browser/app/nsBrowserApp.cpp
+++ b/browser/app/nsBrowserApp.cpp
@@ -149,19 +149,30 @@ static bool IsArg(const char* arg, const
 #endif
 
   return false;
 }
 
 Bootstrap::UniquePtr gBootstrap;
 
 static int do_main(int argc, char* argv[], char* envp[]) {
+  // Allow profile downgrade for Zotero
+  _putenv_s("MOZ_ALLOW_DOWNGRADE", "1");
+  // Don't create dedicated profile (default-esr)
+  _putenv_s("MOZ_LEGACY_PROFILES", "1");
+
   // Allow firefox.exe to launch XULRunner apps via -app <application.ini>
   // Note that -app must be the *first* argument.
-  const char* appDataFile = getenv("XUL_APP_FILE");
+  UniqueFreePtr<char> iniPath = BinaryPath::GetApplicationIni();
+  if (!iniPath) {
+	  Output("Couldn't find application.ini.\n");
+	  return 255;
+
+  }
+  char *appDataFile = iniPath.get();
   if ((!appDataFile || !*appDataFile) && (argc > 1 && IsArg(argv[1], "app"))) {
     if (argc == 2) {
       Output("Incorrect number of arguments passed to -app");
       return 255;
     }
     appDataFile = argv[2];
 
     char appEnv[MAXPATHLEN];
diff --git a/xpcom/build/BinaryPath.h b/xpcom/build/BinaryPath.h
--- a/xpcom/build/BinaryPath.h
+++ b/xpcom/build/BinaryPath.h
@@ -267,16 +267,43 @@ class BinaryPath {
     if (NS_FAILED(Get(path))) {
       return nullptr;
     }
     UniqueFreePtr<char> result;
     result.reset(strdup(path));
     return result;
   }
 
+  static UniqueFreePtr<char> GetApplicationIni() {
+	char path[MAXPATHLEN];
+	if (NS_FAILED(Get(path))) {
+		return nullptr;
+	}
+
+	char *c = path + strlen(path);
+	while (c >= path && *c != '\\' && *c != '/') {
+		*c = NULL;
+		c--;
+	}
+
+	if (c < path) {
+		return nullptr;
+	}
+
+	char iniPath[MAXPATHLEN];
+	int n = snprintf(iniPath, MAXPATHLEN, "%s\\app\\application.ini", path);
+	if (n < 0 || n >= MAXPATHLEN) {
+		return nullptr;
+	}
+
+	UniqueFreePtr<char> result;
+	result.reset(strdup(iniPath));
+	return result;
+  }
+
 #ifdef MOZILLA_INTERNAL_API
   static nsresult GetFile(nsIFile** aResult) {
     nsCOMPtr<nsIFile> lf;
 #  ifdef XP_WIN
     wchar_t exePath[MAXPATHLEN];
     nsresult rv = GetW(exePath);
 #  else
     char exePath[MAXPATHLEN];