diff --git a/WebApp/src/uk/ac/exeter/QuinCe/web/Progress.java b/WebApp/src/uk/ac/exeter/QuinCe/web/Progress.java
index 74c9ea707..5524822e1 100644
--- a/WebApp/src/uk/ac/exeter/QuinCe/web/Progress.java
+++ b/WebApp/src/uk/ac/exeter/QuinCe/web/Progress.java
@@ -57,11 +57,15 @@ public void setMax(float max) {
    *          The value.
    */
   public void setValue(float value) {
-    this.value = value;
+    synchronized (this) {
+      this.value = value;
+    }
   }
 
   public void increment() {
-    this.value += 1;
+    synchronized (this) {
+      this.value += 1;
+    }
   }
 
   /**