Index: trunk/psModules/src/imcombine/pmStackReject.c
===================================================================
--- trunk/psModules/src/imcombine/pmStackReject.c	(revision 20633)
+++ trunk/psModules/src/imcombine/pmStackReject.c	(revision 20832)
@@ -258,4 +258,7 @@
     }
 #endif
+
+    // Need to set psImageConvolveMask threading OFF because that would generate threads on top of threads
+    bool oldThreads = psImageConvolveSetThreads(false); // Old value of threading for psImageColvolve
 
     psImage *target = psImageRecycle(convolved, numCols, numRows, PS_TYPE_MASK); // Grown image
@@ -330,4 +333,6 @@
     }
 
+    psImageConvolveSetThreads(oldThreads);
+
 #ifdef TESTING
     {