diff -r 978b7ea3e3ee -r 108e815fdc8e src/Pure/build-jars
--- a/src/Pure/build-jars	Fri May 20 23:59:46 2011 +0200
+++ b/src/Pure/build-jars	Sat May 21 00:00:14 2011 +0200
@@ -2,7 +2,7 @@
 #
 # Author: Makarius
 #
-# mk-jars - build Isabelle/Scala
+# build-jars - build Isabelle/Scala
 #
 # Requires proper Isabelle settings environment.
 
@@ -15,7 +15,7 @@
   exit 2
 }
 
-[ -n "$ISABELLE_HOME" ] || fail "Missing Isabelle settings environment"
+[ -z "$ISABELLE_HOME" ] && fail "Missing Isabelle settings environment"
 [ -z "$SCALA_HOME" ] && fail "Unknown SCALA_HOME -- Scala unavailable"