diff --git a/core/src/net/sf/openrocket/gui/simulation/SimulationWarningDialog.java b/core/src/net/sf/openrocket/gui/simulation/SimulationWarningDialog.java
index 45a9bfa80..d9625cb17 100644
--- a/core/src/net/sf/openrocket/gui/simulation/SimulationWarningDialog.java
+++ b/core/src/net/sf/openrocket/gui/simulation/SimulationWarningDialog.java
@@ -17,7 +17,7 @@ public class SimulationWarningDialog {
 	
 	public static void showWarningDialog(Component parent, Simulation simulation) {
 		
-		if (simulation.getSimulatedWarnings().size() > 0) {
+		if (simulation.getSimulatedWarnings() != null && simulation.getSimulatedWarnings().size() > 0) {
 			ArrayList<String> messages = new ArrayList<String>();
 			messages.add(trans.get("SimuRunDlg.msg.errorOccurred"));
 			for (Warning m : simulation.getSimulatedWarnings()) {