Index: trunk/ppStack/src/ppStackCamera.c
===================================================================
--- trunk/ppStack/src/ppStackCamera.c	(revision 13613)
+++ trunk/ppStack/src/ppStackCamera.c	(revision 13666)
@@ -34,5 +34,6 @@
         }
 
-        psString mask = psMetadataLookupStr(NULL, input, "MASK"); // Name of mask
+        bool mdok;
+        psString mask = psMetadataLookupStr(&mdok, input, "MASK"); // Name of mask
 
         float seeing = psMetadataLookupF32(NULL, input, "SEEING"); // Seeing FWHM
@@ -106,5 +107,7 @@
     psFree(iter);
     psMetadataRemoveKey(config->arguments, "IMAGE.FILENAMES");
-    psMetadataRemoveKey(config->arguments, "MASK.FILENAMES");
+    if (psMetadataLookup(config->arguments, "MASK.FILENAMES")) {
+        psMetadataRemoveKey(config->arguments, "MASK.FILENAMES");
+    }
 
     psMetadataAddS32(config->arguments, PS_LIST_TAIL, "INPUTS.NUM", 0, "Number of input files", i);