diff --git a/tlatools/src/tlc2/TLC.java b/tlatools/src/tlc2/TLC.java
index 48c2d52d337a4c25b26deff4be391a1b67f0d64a..3d180a7ca1c0c954709df872b1db3265b382a25d 100644
--- a/tlatools/src/tlc2/TLC.java
+++ b/tlatools/src/tlc2/TLC.java
@@ -415,7 +415,7 @@ public class TLC {
             	
                 TLCGlobals.tool = true;
                 
-                if (args[index].equals("nomonolith")) {
+                if ((index < args.length) && args[index].equals("nomonolith")) {
                 	index++;
                 	avoidMonolithSpecTECreation = true;
                 }