diff --git a/bwapy/libbwapy.pyx b/bwapy/libbwapy.pyx
index 30642e5..151ca5f 100644
--- a/bwapy/libbwapy.pyx
+++ b/bwapy/libbwapy.pyx
@@ -299,12 +299,12 @@ cdef class BwaAln:
         rec.cigarstring = cigar
 
         # # tags
-        # attrs = dict()
-        # if seq.type != BWA_TYPE_NO_MATCH:
-        #     attrs["MD"] = bwa_cal_md1(seq.n_cigar, seq.cigar, seq.len, seq.pos,
-        #                               seq.rseq if seq.strand else seq.seq, self._index._bns.l_pac,
-        #                               self._pacseq, kstr, &nm)
-        # rec.set_tags(list(attrs.items()))
+        if seq.type != BWA_TYPE_NO_MATCH:
+            attrs = dict()
+            attrs["MD"] = bwa_cal_md1(seq.n_cigar, seq.cigar, seq.len, seq.pos,
+                                      seq.rseq if seq.strand else seq.seq, self._index._bns.l_pac,
+                                      self._pacseq, kstr, &nm)
+            rec.set_tags(list(attrs.items()))
         # # TODO:the custom bwa tags: XT, NM, XN, SM, AM, X0, X1, XM, XO, XG, XA, HN
 
         return rec