diff --git a/README.md b/README.md
index 8526010..e53dd36 100644
--- a/README.md
+++ b/README.md
@@ -77,3 +77,7 @@ echo($f1->compute()."<br>\n"); //7.071...
 
 * Would be better to give parameters in the compute, to allow one parsing -many compute with differente variable values, but needs rewrite of current parse-compute split.
 * The index of indexed arrays should be evaluated to allow formulas as indexes, but needs rewrite of current parse-compute split.
+
+##Known bugs
+* Won't allow unari operator directly binary operator like "5*-x" or "5+-x". 
+  Your can workaround by using parenthesis like "5*(-x)" or "5+(-x)"