diff --git a/docs/manual/part2-6.txt b/docs/manual/part2-6.txt
index 7a44943..62dcf64 100644
--- a/docs/manual/part2-6.txt
+++ b/docs/manual/part2-6.txt
@@ -16,6 +16,7 @@ It can take three options:
 * ``error`` - stop and raise an exception (default)
 * ``ignore`` - keep data from the original that contains data at overlapped address
 * ``replace`` - use data from the new object that contains data at overlapped address
+* ``identical`` - raise an exception if data is different
 
 You can merge only part of other hex file by using slice index notation::
 
diff --git a/docs/manual/part3-4.txt b/docs/manual/part3-4.txt
index 7b5b8b8..2205261 100644
--- a/docs/manual/part3-4.txt
+++ b/docs/manual/part3-4.txt
@@ -22,6 +22,8 @@ This is a script to merge two different hex files. It is a frontend for the
                                             contains data at overlapped address
                                 * replace -- use data from last file that
                                              contains data at overlapped address
+                                * identical -- raise error if data differ
+
 
     Arguments:
         FILES       list of hex files for merging
diff --git a/intelhex/__init__.py b/intelhex/__init__.py
index 091b5ab..c96998a 100644
--- a/intelhex/__init__.py
+++ b/intelhex/__init__.py
@@ -853,7 +853,9 @@ def merge(self, other, overlap='error'):
                         - ignore: ignore other data and keep current data
                                   in overlapping region;
                         - replace: replace data with other data
-                                  in overlapping region.
+                                  in overlapping region;
+                        - identical: raising OverlapError if data is not
+                                  identical.
 
         @raise  TypeError       if other is not instance of IntelHex
         @raise  ValueError      if other is the same object as self 
@@ -866,9 +868,9 @@ def merge(self, other, overlap='error'):
             raise TypeError('other should be IntelHex object')
         if other is self:
             raise ValueError("Can't merge itself")
-        if overlap not in ('error', 'ignore', 'replace'):
+        if overlap not in ('error', 'ignore', 'replace', 'identical'):
             raise ValueError("overlap argument should be either "
-                "'error', 'ignore' or 'replace'")
+                "'error', 'ignore', 'replace' or 'identical'")
         # merge data
         this_buf = self._buf
         other_buf = other._buf
@@ -879,6 +881,9 @@ def merge(self, other, overlap='error'):
                         'Data overlapped at address 0x%X' % i)
                 elif overlap == 'ignore':
                     continue
+                elif overlap == 'identical' and this_buf[i] != other_buf[i]:
+                    raise AddressOverlapError(
+                        'Data at address 0x%X is different: 0x%X vs. 0x%X' % (i, this_buf[i], other_buf[i]))
             this_buf[i] = other_buf[i]
         # merge start_addr
         if self.start_addr != other.start_addr:
diff --git a/intelhex/scripts/hexmerge.py b/intelhex/scripts/hexmerge.py
index 8be98e8..350b55f 100755
--- a/intelhex/scripts/hexmerge.py
+++ b/intelhex/scripts/hexmerge.py
@@ -57,6 +57,8 @@
                                         contains data at overlapped address
                             * replace -- use data from last file that
                                          contains data at overlapped address
+                            * identical -- if overlapped data verifies that values
+                                       are identical
 
 Arguments:
     FILES       list of hex files for merging
@@ -122,7 +124,7 @@ def main(args=None):
             elif o == '--no-start-addr':
                 write_start_addr = False
             elif o == '--overlap':
-                if a in ('error', 'ignore', 'replace'):
+                if a in ('error', 'ignore', 'replace', 'identical'):
                     overlap = a
                 else:
                     raise getopt.GetoptError('Bad overlap value')
diff --git a/intelhex/test.py b/intelhex/test.py
index df89276..90bd694 100755
--- a/intelhex/test.py
+++ b/intelhex/test.py
@@ -1171,7 +1171,7 @@ def test_merge_wrong_args(self):
             ih1.merge, ih1)
         ih2 = IntelHex()
         self.assertRaisesMsg(ValueError, "overlap argument should be either "
-            "'error', 'ignore' or 'replace'",
+            "'error', 'ignore', 'replace' or 'identical'",
             ih1.merge, ih2, overlap='spam')
 
     def test_merge_overlap(self):
@@ -1191,6 +1191,17 @@ def test_merge_overlap(self):
         ih2 = IntelHex({0:2})
         ih1.merge(ih2, overlap='replace')
         self.assertEqual({0:2}, ih1.todict())
+        # identical: same value: ok
+        ih1 = IntelHex({0:1})
+        ih2 = IntelHex({0:1})
+        ih1.merge(ih2, overlap='identical')
+        self.assertEqual({0:1}, ih1.todict())
+        # identical: different value: raise error
+        ih1 = IntelHex({0:1})
+        ih2 = IntelHex({0:2})
+        self.assertRaisesMsg(intelhex.AddressOverlapError,
+            'Data at address 0x0 is different: 0x1 vs. 0x2',
+            ih1.merge, ih2, overlap='identical')
 
     def test_merge_start_addr(self):
         # this, None