diff --git a/prism/etc/scripts/prism-auto b/prism/etc/scripts/prism-auto
index 6251d49d..0189926d 100755
--- a/prism/etc/scripts/prism-auto
+++ b/prism/etc/scripts/prism-auto
@@ -668,6 +668,8 @@ if options.logDir and not os.path.isdir(options.logDir):
     print "Log directory \"" + options.logDir + "\" does not exist"
     sys.exit(1)
 if options.nailgun:
+    exitCode = subprocess.Popen([options.ngprism, "--nailgun-help"], stderr=open(os.devnull, 'w')).wait()
+    print exitCode
     os.system(options.prismExec + " -ng &")
     time.sleep(0.5)
 for arg in args:
diff --git a/prism/src/parser/BooleanUtils.java b/prism/src/parser/BooleanUtils.java
index e5c3183e..31e2ea27 100644
--- a/prism/src/parser/BooleanUtils.java
+++ b/prism/src/parser/BooleanUtils.java
@@ -133,7 +133,7 @@ public class BooleanUtils
 					return Expression.Or(Expression.Not(a), b);
 				}
 				// Remove iff: a <=> b
-				if (Expression.isImplies(e)) {
+				if (Expression.isIff(e)) {
 					Expression a = (Expression)(e.getOperand1().accept(this));
 					Expression b = (Expression)(e.getOperand2().accept(this));
 					// a <=> b  ==  (a | !b) & (!a | b)