diff --git a/lib/controller/checks.py b/lib/controller/checks.py
index 79090fb7d..fbc48c02c 100644
--- a/lib/controller/checks.py
+++ b/lib/controller/checks.py
@@ -292,7 +292,7 @@ def checkStability():
             checkDynamicContent(firstPage, secondPage)
 
             if not Request.queryPage():
-                errMsg  = "target url is too dynamic. unable to continue. consider using other methods"
+                errMsg  = "target url is too dynamic. unable to continue. consider using other switches (e.g. --longest-common, --string, --text-only, etc.)"
                 logger.error(errMsg)
                 raise sqlmapSilentQuitException
 
diff --git a/lib/core/option.py b/lib/core/option.py
index ae22b1f21..583ec56c5 100644
--- a/lib/core/option.py
+++ b/lib/core/option.py
@@ -1238,6 +1238,10 @@ def __basicOptionValidation():
         errMsg = "switch --text-only is incompatible with switch --null-connection"
         raise sqlmapSyntaxException, errMsg
 
+    if conf.longestCommon and conf.nullConnection:
+        errMsg = "switch --longest-common is incompatible with switch --null-connection"
+        raise sqlmapSyntaxException, errMsg
+
     if conf.data and conf.nullConnection:
         errMsg = "switch --data is incompatible with switch --null-connection"
         raise sqlmapSyntaxException, errMsg