diff --git a/umi_tools/sam_methods.py b/umi_tools/sam_methods.py
index 79a577a..871dbf6 100644
--- a/umi_tools/sam_methods.py
+++ b/umi_tools/sam_methods.py
@@ -605,7 +605,7 @@ def write_mates(self):
             U.debug("Dumping %i mates for contig %s" % (
                 len(self.read1s), self.chrom))
 
-        for read in self.infile.fetch(reference=self.chrom, multiple_iterators=True):
+        for read in self.mate_file.fetch(reference=self.chrom, multiple_iterators=False):
             if any((read.is_unmapped, read.mate_is_unmapped, read.is_read1)):
                 continue
 
@@ -625,7 +625,7 @@ def close(self):
                len(self.read1s))
 
         found = 0
-        for read in self.infile.fetch(until_eof=True, multiple_iterators=True):
+        for read in self.mate_file.fetch(until_eof=True, multiple_iterators=True):
 
             if any((read.is_unmapped, read.mate_is_unmapped, read.is_read1)):
                 continue