Index: trunk/Ohana/src/libdvo/src/cmf-ps1-v1-alt.c
===================================================================
--- trunk/Ohana/src/libdvo/src/cmf-ps1-v1-alt.c	(revision 29439)
+++ trunk/Ohana/src/libdvo/src/cmf-ps1-v1-alt.c	(revision 29537)
@@ -1,3 +1,10 @@
 # include "dvo.h"
+
+/* if we are not correctly including the ohana headers, this will fail */
+# ifndef BYTE_SWAP
+# ifndef NOT_BYTE_SWAP
+# error "neither BYTE_SWAP not NOT_BYTE_SWAP is set"
+# endif
+# endif
 
 CMF_PS1_V2 *gfits_table_get_CMF_PS1_V1_Alt (FTable *ftable, off_t *Ndata, char *swapped) {