diff --git a/tools/bin/cassandra.in.sh b/tools/bin/cassandra.in.sh
index 5d265d40f9..d2b199c3fa 100644
--- a/tools/bin/cassandra.in.sh
+++ b/tools/bin/cassandra.in.sh
@@ -30,10 +30,18 @@ CLASSPATH="$CASSANDRA_CONF"
 # compiled classes. NOTE: This isn't needed by the startup script,
 # it's just used here in constructing the classpath.
 if [ -d $CASSANDRA_HOME/build ] ; then
-    #cassandra_bin="$CASSANDRA_HOME/build/classes/main"
-    cassandra_bin=`ls -1 $CASSANDRA_HOME/build/apache-cassandra*.jar`
-    cassandra_bin="$cassandra_bin:$CASSANDRA_HOME/build/classes/stress:$CASSANDRA_HOME/build/classes/fqltool"
-    CLASSPATH="$CLASSPATH:$cassandra_bin"
+    jars_cnt="`ls -1 $CASSANDRA_HOME/build/apache-cassandra*.jar | grep -v 'javadoc.jar' | grep -v 'sources.jar' | wc -l | xargs echo`"
+    if [ "$jars_cnt" -gt 1 ]; then
+        dir="`cd $CASSANDRA_HOME/build; pwd`"
+        echo "There are JAR artifacts for multiple versions in the $dir directory. Please clean the project with 'ant realclean' and build it again." 1>&2
+        exit 1
+    fi
+
+    if [ "$jars_cnt" = "1" ]; then
+        cassandra_bin="`ls -1 $CASSANDRA_HOME/build/apache-cassandra*.jar | grep -v javadoc | grep -v sources`"
+        cassandra_bin="$cassandra_bin:$CASSANDRA_HOME/build/classes/stress:$CASSANDRA_HOME/build/classes/fqltool"
+        CLASSPATH="$CLASSPATH:$cassandra_bin"
+    fi
 fi
 
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