diff --git a/orthofinder/scripts/blast_file_processor.py b/orthofinder/scripts/blast_file_processor.py
index de669e0d93c9557be766ddcb0903b2b84b234ae3..d28af715ce5664acc7525d35515c4f03fca8c09d 100644
--- a/orthofinder/scripts/blast_file_processor.py
+++ b/orthofinder/scripts/blast_file_processor.py
@@ -145,6 +145,8 @@ def WriteNormalizedBlastFile(blastDir_list, B, iSpecies, jSpecies, sep = "_", qD
                     sys.stderr.write("\nERROR: Matrix index : %s \n" % e)
                     pass
                 blastwriter.writerow(row)
+            tempfile.flush()
+            tempfile.close()
             move(tempfile.name, fnNorm)
     except Exception:
         sys.stderr.write("Malformatted line in %sBlast%d_%d.txt\nOffending line was:\n" % (d, iSpecies, jSpecies))