Index: trunk/ppMerge/src/ppMergeArguments.c
===================================================================
--- trunk/ppMerge/src/ppMergeArguments.c	(revision 18757)
+++ trunk/ppMerge/src/ppMergeArguments.c	(revision 18758)
@@ -171,4 +171,5 @@
     }
 
+# if (THREADED)
     // Number of threads
     if ((argnum = psArgumentGet(argc, argv, "-threads"))) {
@@ -182,4 +183,5 @@
 	psThreadPoolInit (nThreads, &ppMergeThreadLauncher);
     }
+# endif
 
     if (argc == 1 || !psArgumentParse(arguments, &argc, argv) || argc != 3) {