--- a/netwerk/protocol/http/nsHttpHandler.cpp
+++ b/netwerk/protocol/http/nsHttpHandler.cpp
@@ -313,16 +313,23 @@ nsHttpHandler::nsHttpHandler()
 void
 nsHttpHandler::SetFastOpenOSSupport()
 {
     mFastOpenSupported = false;
 #if !defined(XP_WIN) && !defined(XP_LINUX) && !defined(ANDROID) && !defined(HAS_CONNECTX)
     return;
 #elif defined(XP_WIN)
     mFastOpenSupported = IsWindows10BuildOrLater(16299);
+
+    if (mFastOpenSupported) {
+        // We have some problems with lavasoft software and tcp fast open.
+        if (GetModuleHandleW(L"pmls64.dll") || GetModuleHandleW(L"rlls64.dll")) {
+            mFastOpenSupported = false;
+        }
+    }
 #else
 
     nsAutoCString version;
     nsresult rv;
 #ifdef ANDROID
     nsCOMPtr<nsIPropertyBag2> infoService =
         do_GetService("@mozilla.org/system-info;1");
     MOZ_ASSERT(infoService, "Could not find a system info service");