Index: trunk/ppStack/src/ppStackUpdateHeader.c
===================================================================
--- trunk/ppStack/src/ppStackUpdateHeader.c	(revision 34800)
+++ trunk/ppStack/src/ppStackUpdateHeader.c	(revision 35868)
@@ -98,4 +98,7 @@
 
 	float value = options->norm ? pow(10.0, -0.4*options->norm->data.F32[i]) : NAN;
+	if ((options->inputMask)&&(options->inputMask->data.PS_TYPE_VECTOR_MASK_DATA[i])) {
+	  value = 0.0; // If this is NAN, then it's recorded in the header as a character string instead of a float.
+	}
 	snprintf (field, 64, "SCL_%04d", i);
 	psMetadataAddF32(hdu->header, PS_LIST_TAIL, field, PS_META_REPLACE, "input image scale factor", value);
@@ -132,4 +135,5 @@
 	expROhdu->header = psMetadataAlloc();
       }
+
       expRO->parent->parent->parent->hdu->header = psMetadataCopy(expRO->parent->parent->parent->hdu->header,
 								  outRO->parent->parent->parent->hdu->header);