diff --git a/python_source/voidUtil/catalogUtil.py b/python_source/voidUtil/catalogUtil.py
index 9adacf0..c189bb3 100644
--- a/python_source/voidUtil/catalogUtil.py
+++ b/python_source/voidUtil/catalogUtil.py
@@ -100,7 +100,13 @@ def loadPart(sampleDir):
       uniqueID = np.fromfile(File, dtype=np.int64,count=Np)
       chk = np.fromfile(File, dtype=np.int32,count=1)
 
+    ## TEST - outputting of mock particles is temporary for debugging
+    mockPart = []
     if isObservation == 1:
+      mockPartx = x[maskIndex+1:Np]
+      mockParty = y[maskIndex+1:Np]
+      mockPartz = z[maskIndex+1:Np]
+
       x = x[0:maskIndex]# * 100/300000
       y = y[0:maskIndex]# * 100/300000
       z = z[0:maskIndex]# * 100/300000
@@ -110,8 +116,8 @@ def loadPart(sampleDir):
       uniqueID = uniqueID[0:maskIndex]
 
     partData = np.column_stack((x,y,z))
-
     extraData = np.column_stack((RA,Dec,redshift,uniqueID))
+    mockPart = np.column_stack((mockPartx, mockParty, mockPartz))
 
     boxLen = mul
 
@@ -138,7 +144,7 @@ def loadPart(sampleDir):
 
     isObservationData = isObservation == 1
 
-    return partData, boxLen, volNorm, isObservationData, ranges, extraData
+    return partData, boxLen, volNorm, isObservationData, ranges, extraData, mockPart
 
 # -----------------------------------------------------------------------------
 def getVolNorm(sampleDir):
@@ -434,10 +440,11 @@ def loadVoidCatalog(sampleDir, dataPortion="central", loadParticles=True,
 
   if loadParticles:
     print("Loading all particles...")
-    partData, boxLen, volNorm, isObservationData, ranges, extraData = loadPart(sampleDir)
+    partData, boxLen, volNorm, isObservationData, ranges, extraData, mockPart = loadPart(sampleDir)
     numPartTot = len(partData)
     catalog.numPartTot = numPartTot
     catalog.partPos = partData
+    catalog.mockPart = mockPart
     catalog.part = []
     for i in range(len(partData)):
       catalog.part.append(Bunch(x = partData[i][0],
@@ -540,8 +547,10 @@ def loadVoidCatalog(sampleDir, dataPortion="central", loadParticles=True,
     print(" Matching particles to voids...")
     for void in catalog.voids:
       voidID = void.voidID
-      for zoneID in catalog.void2Zones[voidID].zoneIDs:
-        for partID in catalog.zones2Parts[zoneID].partIDs:
+      for iZ in range(catalog.void2Zones[voidID].numZones):
+        zoneID = catalog.void2Zones[voidID].zoneIDs[iZ]
+        for p in range(catalog.zones2Parts[zoneID].numPart):
+          partID = catalog.zones2Parts[zoneID].partIDs[p]
           catalog.part[partID].voidID = voidID
 
     print("Done loading catalog.")