diff --git a/src/som/interpreter/nodes/ExpressionNode.java b/src/som/interpreter/nodes/ExpressionNode.java
index b6409209d..817a641ea 100644
--- a/src/som/interpreter/nodes/ExpressionNode.java
+++ b/src/som/interpreter/nodes/ExpressionNode.java
@@ -166,6 +166,6 @@ public WrapperNode createWrapper(final ProbeNode probe) {
 
   @Override
   public String toString() {
-    return getClass().getSimpleName() + "(" + sourceSection.toString() + ")";
+    return getClass().getSimpleName() + "(" + String.valueOf(sourceSection) + ")";
   }
 }