diff --git a/src/net/mc_pandacraft/java/plugin/pandacraftutils/calculator/CalculatorManager.java b/src/net/mc_pandacraft/java/plugin/pandacraftutils/calculator/CalculatorManager.java
index 1403336..b39cb26 100644
--- a/src/net/mc_pandacraft/java/plugin/pandacraftutils/calculator/CalculatorManager.java
+++ b/src/net/mc_pandacraft/java/plugin/pandacraftutils/calculator/CalculatorManager.java
@@ -55,6 +55,10 @@ public class CalculatorManager implements Listener {
 				event.getPlayer().sendMessage(ChatColor.GRAY+"res"+i+ChatColor.RESET+" : "+ChatColor.GRAY+el.expression+ChatColor.RESET+"="+ChatColor.GRAY+el.value);
 				i--;
 			}
+			if (history.get(event.getPlayer()).size() == 0)
+			{
+				event.getPlayer().sendMessage(ChatColor.RED+"Utilisez le symbole "+ChatColor.GRAY+"="+ChatColor.RED+" dans le chat pour faire un calcul mathématique");
+			}
 		}
 		else
 		{
@@ -80,7 +84,7 @@ public class CalculatorManager implements Listener {
 			}
 			catch (IllegalArgumentException e) {
 				event.getPlayer().sendMessage(ChatColor.RED+e.getMessage());
-				
+				event.getPlayer().sendMessage(ChatColor.RED+"Utilisez le symbole "+ChatColor.GRAY+"="+ChatColor.RED+" dans le chat pour faire un calcul mathématique");
 			}
 			
 		}
diff --git a/src/net/mc_pandacraft/java/util/JArithmeticInterpreter.java b/src/net/mc_pandacraft/java/util/JArithmeticInterpreter.java
index ff8e6f9..2230f6f 100644
--- a/src/net/mc_pandacraft/java/util/JArithmeticInterpreter.java
+++ b/src/net/mc_pandacraft/java/util/JArithmeticInterpreter.java
@@ -735,7 +735,11 @@ public class JArithmeticInterpreter {
 	{
 		StringBuffer input = new StringBuffer(expr);
 
-		JArithmeticInterpreter jai = JArithmeticInterpreter.constructTree(input,input.length(),0);
+		JArithmeticInterpreter jai = null;
+		
+		try {
+			jai = JArithmeticInterpreter.constructTree(input,input.length(),0);
+		} catch (Exception e) {  }
 		
 		if (jai==null)
 			throw new IllegalArgumentException("Le calcul passé en paramètre est invalide");