Index: uspace/lib/posix/stdio.h
===================================================================
--- uspace/lib/posix/stdio.h	(revision 2a53f7165baaf7867d2c714d76153b28c9028386)
+++ uspace/lib/posix/stdio.h	(revision c67aff2b73c9636ea0c229cdbf3bfc48af966545)
@@ -127,4 +127,10 @@
 
 #ifndef LIBPOSIX_INTERNAL
+	/* DEBUG macro does not belong to POSIX stdio.h. Its unconditional
+	 * definition in the native stdio.h causes unexpected behaviour of
+	 * applications which uses their own DEBUG macro (e.g. debugging
+	 * output is printed even if not desirable). */
+	#undef DEBUG
+
 	#define ctermid posix_ctermid