diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4c67153b1..526b077a8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,8 @@ Bugfixes and improvements:
 - For the external scores, Mikado can now accept any type of numerical or boolean value. Mikado will understand at serialisation time whether a particular score can be used raw (ie its values are strictly comprised between 0 and 1) or whether it has to be forcibly scaled.
   - This allows Mikado to use e.g. transcript expression as a valid metric.
 - Now coding and non-coding transcripts will be in different loci.
+- Corrected a bug in the calculation of overlapping intervals during BLAST serialisation.
+- Now BLAST HSPs will have stored as well whether there is an in-frame stop codon.
 - Mikado prepare now can accept models that lack any exon features but still have valid CDS/UTR features - this is necessary for some protein prediction tools.
 - Fixed [#139](https://github.com/lucventurini/mikado/issues/139): Mikado was reverse complementing non-uppercase letters incorrectly.
 - [#135](https://github.com/lucventurini/mikado/issues/135): Mikado so far operated under the assumption that the 8th field in GTF files was the **frame**, not the **phase** like in GFF3s. This is actually incompatible with EnsEMBL and many widespread tools such as [GenomeTools](http://genometools.org/) or [GffRead](https://github.com/gpertea/gffread). Starting from this version, Mikado uniforms with these other tools.
diff --git a/Mikado/parsers/blast_utils.py b/Mikado/parsers/blast_utils.py
index 732bb53ab..81157f665 100644
--- a/Mikado/parsers/blast_utils.py
+++ b/Mikado/parsers/blast_utils.py
@@ -293,9 +293,6 @@ def __calculate_merges(intervals: np.array):
     :return:
     """
 
-    if intervals.shape[1] != 2:
-        raise ValueError("Invalid array shape: {}".format(intervals.shape))
-
     if intervals.shape[0] == 1:
         return intervals
 
@@ -343,7 +340,17 @@ def merge(intervals: [(int, int)], query_length=None, offset=1):
 
     # Assume tuple of the form (start,end)
     # Create array and sort
-    intervals = np.array([sorted(_) for _ in intervals], dtype=np.int)
+    offset = int(offset)
+    if offset not in [0, 1]:
+        raise ValueError("Invalid offset - only 0 and 1 allowed: {}".format(offset))
+
+    try:
+        intervals = np.array([sorted(_) for _ in intervals], dtype=np.int)
+        if intervals.shape[1] != 2:
+            raise ValueError("Invalid shape for intervals: {}".format(intervals.shape))
+    except (TypeError, ValueError):
+        raise TypeError("Invalid array for intervals: {}".format(intervals))
+
     intervals = intervals[np.lexsort((intervals[:,1], intervals[:,0]))]
     intervals = __calculate_merges(intervals)
     total_length_covered = int(abs(intervals[:,1] - intervals[:,0] + offset).sum())
diff --git a/Mikado/tests/test_blast_related.py b/Mikado/tests/test_blast_related.py
index b66e73737..1aa1ba116 100644
--- a/Mikado/tests/test_blast_related.py
+++ b/Mikado/tests/test_blast_related.py
@@ -7,7 +7,7 @@
 import os
 import gzip
 import subprocess
-import shutil
+from Mikado.serializers.blast_serializer import utils as seri_blast_utils
 import time
 
 
@@ -124,5 +124,62 @@ def test_asn(self):
         os.remove(valid_asn)
         os.chdir(master)
 
+
+class TestMerging(unittest.TestCase):
+
+    """Small class to test basic cases of the merging algorithm."""
+
+    def test_merging_1(self):
+
+        l = [(-10, -5), (-6, 8), (5, 10), (20, 40)]
+        tot_length = 51
+        corr_merged = [(-10, 10), (20, 40)]
+        merged, tot_length = seri_blast_utils.merge(l, query_length=tot_length, offset=1)
+        self.assertEqual(merged, corr_merged)
+        self.assertEqual(tot_length, 10 - -10 +1 + 40 - 20 + 1)
+
+    def test_merging_2(self):
+
+        l = [(100, 200)]
+        for offset in [0, 1, 2]:
+            with self.subTest(offset=offset):
+                tot_length = l[0][1] - l[0][0] + offset
+                if offset == 2:
+                    with self.assertRaises(ValueError):
+                        _ = seri_blast_utils.merge(l, offset=offset)
+                else:
+                    merged, length = seri_blast_utils.merge(l, offset=offset)
+                    self.assertEqual(length, tot_length)
+                    self.assertEqual(merged, l)
+
+    def test_various_merging(self):
+
+        invalid = [
+            [('a', 0)],
+            [('a', 'b')],
+            [(10, 20), ('a', 'b')],
+            [(10, 20, 30), (40, 50, 60)]
+        ]
+
+        for inv in invalid:
+            with self.subTest(inv=inv):
+                with self.assertRaises(TypeError, msg=inv):
+                    seri_blast_utils.merge(inv)
+
+        valid = {
+            0: [[('10', '20')], [(10, 20)]],
+            1: [[(10, 30)], [(10, 30)]],
+            2: [[(-10.0, 5.5)], [(-10, 5)]],
+            3: [[(-4, -10)], [(-10, -4)]],
+            4: [[(-5, -10), (-2.2, -7.3)], [(-10, -2)]]
+        }
+
+        for val in valid:
+            inp, out = valid[val]
+            with self.subTest(val=val, msg=valid[val]):
+                _ = seri_blast_utils.merge(inp)
+                self.assertEqual(out, _[0])
+
+
 if __name__ == '__main__':
     unittest.main()
\ No newline at end of file