diff --git a/Makefile b/Makefile
index 4891da8..6c4611c 100644
--- a/Makefile
+++ b/Makefile
@@ -128,7 +128,7 @@ help:
 	@echo "Usage: make [all,compile,clean,run,runsky,runesb]"
 
 run:	compile
-	$(JAVA) $(JAVAARGS) se.sics.mspsim.util.IHexReader $(ARGS) $(FIRMWAREFILE) $(MAPFILE)
+	$(JAVA) $(JAVAARGS) se.sics.mspsim.Main $(ARGS) $(FIRMWAREFILE) $(MAPFILE)
 
 runesb:	compile
 	$(JAVA) $(JAVAARGS) se.sics.mspsim.platform.esb.ESBNode $(ARGS) $(ESBFIRMWARE) $(MAPFILE)
diff --git a/build.xml b/build.xml
index b50c524..ed932f9 100644
--- a/build.xml
+++ b/build.xml
@@ -94,7 +94,12 @@
     </java>
   </target>
 
-  <target name="run" depends="runsky"/>
+  <target name="run" depends="jar" description="run MSPSim">
+    <property name="FIRMWAREFILE" value="firmware/sky/blink.sky"/>
+    <java fork="true" classpath="${jarfile}" classname="se.sics.mspsim.Main">
+      <arg value="${FIRMWAREFILE}"/>
+    </java>
+  </target>
 
   <target name="cputest" depends="jar" description="run MSPSim CPU test">
     <property name="FIRMWAREFILE" value="tests/cputest.sky"/>
diff --git a/se/sics/mspsim/Main.java b/se/sics/mspsim/Main.java
index 31b73a9..7270aac 100644
--- a/se/sics/mspsim/Main.java
+++ b/se/sics/mspsim/Main.java
@@ -28,16 +28,12 @@
  *
  * This file is part of MSPSim.
  *
- * $Id$
- *
  * -----------------------------------------------------------------
  *
  * Main
  *
  * Authors : Joakim Eriksson, Niclas Finne
  * Created : 6 nov 2008
- * Updated : $Date$
- *           $Revision$
  */
 
 package se.sics.mspsim;
@@ -104,7 +100,21 @@ public class Main {
     if (nodeType != null) {
       node = createNode(nodeType);
     } else {
-      platform = config.getProperty("platform", "sky");
+      platform = config.getProperty("platform");
+      if (platform == null) {
+          // Default platform
+          platform = "sky";
+
+          // Guess platform based on firmware filename suffix.
+          // TinyOS firmware files are often named 'main.exe'.
+          String[] a = config.getArguments();
+          if (a.length > 0 && !"main.exe".equals(a[0])) {
+              int index = a[0].lastIndexOf('.');
+              if (index > 0) {
+                  platform = a[0].substring(index + 1);
+              }
+          }
+      }
       nodeType = getNodeTypeByPlatform(platform);
       node = createNode(nodeType);
     }