diff --git a/de.prob.ui/src/de/prob/ui/operationview/CustomPreconditionDialogHandler.java b/de.prob.ui/src/de/prob/ui/operationview/CustomPreconditionDialogHandler.java
index c609f3993694cc0267666f2a2fda8c5250be6048..4a1fe38a1462854f92344b39ad88dd6a124f866a 100644
--- a/de.prob.ui/src/de/prob/ui/operationview/CustomPreconditionDialogHandler.java
+++ b/de.prob.ui/src/de/prob/ui/operationview/CustomPreconditionDialogHandler.java
@@ -41,6 +41,7 @@ public class CustomPreconditionDialogHandler extends AbstractHandler implements
 		try {
 			ExecuteOperationCommand
 					.executeOperation(Animator.getAnimator(), op);
+					// TODO: provide feedback when we cannot execute operation
 		} catch (ProBException e) {
 			e.notifyUserOnce();
 		}
diff --git a/de.prob.ui/src/de/prob/ui/operationview/CustomPreconditionInputDialog.java b/de.prob.ui/src/de/prob/ui/operationview/CustomPreconditionInputDialog.java
index eeb0d228f612db767e4f124fadccf47acc2af1d6..4e40f8bcb13e767f406cb71a63fca879bdcc9795 100644
--- a/de.prob.ui/src/de/prob/ui/operationview/CustomPreconditionInputDialog.java
+++ b/de.prob.ui/src/de/prob/ui/operationview/CustomPreconditionInputDialog.java
@@ -56,7 +56,7 @@ public class CustomPreconditionInputDialog extends InputDialog {
 		List<String> params = getOperationParams(op,animator);
 		List<String> vals = op.getArguments();
 		int sze = Math.min(params.size(),vals.size());
-		for (int i = 0; i < sze - 1; i++) {
+		for (int i = 0; i < sze; i++) {
 		    sb.append(params.get(i));
 		    sb.append(" = ");
 		    sb.append(vals.get(i));