Index: trunk/ppMerge/src/ppMergeCombine.c
===================================================================
--- trunk/ppMerge/src/ppMergeCombine.c	(revision 14356)
+++ trunk/ppMerge/src/ppMergeCombine.c	(revision 14797)
@@ -154,5 +154,5 @@
             }
 
-            float shutterRef;           // Reference shutter correction
+            float shutterRef = NAN;     // Reference shutter correction
             if (options->shutter) {
                 shutterRef = pmShutterCorrectionReference(shutters->data[cellNum]);