diff --git a/ChipSeq.py b/ChipSeq.py
index 746c7e4..35f0517 100644
--- a/ChipSeq.py
+++ b/ChipSeq.py
@@ -107,7 +107,7 @@ def sampleReads( self, fragExtract, fragmentSetStr, nReads, generateIntervals ):
         duplicates = np.zeros( N, dtype=np.int )
 
         if generateIntervals:
-            readsToDuplicate = np.zeros( nReads, dtype=np.int )
+            readsToDuplicate = np.zeros( int(nReads), dtype=np.int )
         else:
             readsToDuplicate = []