Index: trunk/psphot/src/pmModelFitSet.c
===================================================================
--- trunk/psphot/src/pmModelFitSet.c	(revision 6379)
+++ trunk/psphot/src/pmModelFitSet.c	(revision 6481)
@@ -42,5 +42,5 @@
     model = params->data.F32[0];
 
-    PAR[0] = 0;
+    PAR[0] = params->data.F32[0];
     for (int i = 0; i < nSrc; i++) {
 	for (int n = 1; n < nPar; n++) {
@@ -53,4 +53,5 @@
 	}
     }
+    deriv->data.F32[0] = dPAR[0]*2.0;
     return (model);
 }