Index: /trunk/Ohana/src/opihi/cmd.astro/fitplx_irls.c
===================================================================
--- /trunk/Ohana/src/opihi/cmd.astro/fitplx_irls.c	(revision 40517)
+++ /trunk/Ohana/src/opihi/cmd.astro/fitplx_irls.c	(revision 40518)
@@ -89,9 +89,16 @@
   if (dDvec->Nelements != Ntotal) ESCAPE ("mis-match in vector lengths (mjd vs dD)  = (%d vs %d)\n", dDvec->Nelements, Ntotal);
   
+  // if mask exists and is an INT, treat as a supplied mask
+  // otherwise, reset
+
   opihi_int *mask = NULL;
   if (mvec) {
-    ResetVector (mvec, OPIHI_INT, Ntotal);
-    mask = mvec->elements.Int;
-    for (i = 0; i < Ntotal; i++) { mask[i] = 1; }
+    if (mvec->type != OPIHI_INT) {
+      ResetVector (mvec, OPIHI_INT, Ntotal);
+      mask = mvec->elements.Int;
+      for (i = 0; i < Ntotal; i++) { mask[i] = 1; }
+    } else {
+      mask = mvec->elements.Int;
+    }
   }