diff --git a/src/main/java/fr/nancy/iut/CalcEngine.java b/src/main/java/fr/nancy/iut/CalcEngine.java
index 14bc40d97f4b0cccda0346dbf1f976bd825c6209..233050f21ad75909796bb866113bb7351fd9ee93 100755
--- a/src/main/java/fr/nancy/iut/CalcEngine.java
+++ b/src/main/java/fr/nancy/iut/CalcEngine.java
@@ -76,6 +76,7 @@ public class CalcEngine
             displayValue = leftOperand - displayValue;
         }
         leftOperand = 0;
+        previousOperator = ' ';
     }
 
     /**
@@ -84,6 +85,7 @@ public class CalcEngine
     public void clear()
     {
         displayValue = 0;
+        previousOperator = ' ';
     }
 
     /**