Index: library/mongodb/example-nx-mongo.tcl
===================================================================
diff -u -r5f281c1ff709a771d08362ee9593dcbe76ebbb2b -ra77464d1f7a06117c621560ec519dc4d387ed5df
--- library/mongodb/example-nx-mongo.tcl	(.../example-nx-mongo.tcl)	(revision 5f281c1ff709a771d08362ee9593dcbe76ebbb2b)
+++ library/mongodb/example-nx-mongo.tcl	(.../example-nx-mongo.tcl)	(revision a77464d1f7a06117c621560ec519dc4d387ed5df)
@@ -12,10 +12,13 @@
 ::nx::mongo::db connect -db "tutorial"
 
 # Make sure, we start always from scratch
+
 nx::mongo::db remove tutorial.persons {}
+if {[::mongo::count [::nx::mongo::db eval {set :mongoConn}] tutorial.persons {}] > 0} {
+  # when we create a capped colletion, we have to use "drop collection" to get rid of it.
+  nx::mongo::db drop collection persons
+}
 
-::mongo::run [::nx::mongo::db eval {set :mongoConn}] tutorial {drop string persons}
-
 #
 # Create the application class "Person"
 #