Index: /trunk/psModules/src/detrend/pmBias.c
===================================================================
--- /trunk/psModules/src/detrend/pmBias.c	(revision 13955)
+++ /trunk/psModules/src/detrend/pmBias.c	(revision 13956)
@@ -487,7 +487,16 @@
         }
 
+	float darkNorm = 1.0;
         float inNorm = pmFPADarkNorm(inRO->parent->parent->parent, view, inTime);
-        float darkNorm = pmFPADarkNorm(darkRO->parent->parent->parent, view, darkTime);
-        if (isnan(inNorm) || isnan(darkNorm)) {
+
+	// if we have a normalized dark exposure, we simply multiply the master by inNorm.  if
+	// we do not have a normalized exposure, we have to scale the master as well.  XXX do
+	// we need to explicitly identify the master as normalized?
+
+	if (darkTime != 1.0) {
+	    darkNorm = pmFPADarkNorm(darkRO->parent->parent->parent, view, darkTime);
+	}
+
+	if (isnan(inNorm) || isnan(darkNorm)) {
             psError(PS_ERR_UNKNOWN, false, "Unable to determine dark normalisations.");
             return false;