diff --git a/mutalyzer/variantchecker.py b/mutalyzer/variantchecker.py
index 0268b5d0f3343fd1ff9cf2885a8925b57abfd657..4068cba0424ad8aa16e241d76a88c941d72e71dc 100644
--- a/mutalyzer/variantchecker.py
+++ b/mutalyzer/variantchecker.py
@@ -36,6 +36,7 @@ class _NotDNAError(_RawVariantError): pass
 class _PositionsNotConsecutiveError(_RawVariantError): pass
 class _LengthMismatchError(_RawVariantError): pass
 class _ReferenceMismatchError(_RawVariantError): pass
+class _RangeInsertionError(_RawVariantError): pass
 class _OffsetSignError(_RawVariantError):
     def __init__(self, main, offset, acceptor):
         self.main = main
@@ -136,9 +137,9 @@ def _check_argument(argument, reference, first, last, output):
 
     @raise _LengthMismatchError: The argument is a length, but it does not
                                  match the given range length.
-    @raise NotDNAError: The argument should be DNA, but it is not.
-    @raise ReferenceMismatchError: The argument is DNA, but it does not
-                                   match the given reference.
+    @raise _NotDNAError: The argument should be DNA, but it is not.
+    @raise _ReferenceMismatchError: The argument is DNA, but it does not
+                                    match the given reference.
     """
     if not argument:
         # The argument is optional, if it is not present, it is correct.
@@ -1047,6 +1048,14 @@ def process_raw_variant(mutator, variant, record, transcript, output):
     if variant.MutationType in ['del', 'dup', 'subst', 'delins']:
         _check_argument(argument, mutator.orig, first, last, output)
 
+    # Check if the inserted sequence is not a range.
+    # Todo: Implement this feature.
+    if variant.MutationType in ['ins', 'delins']:
+        if not argument:
+            output.addMessage(__file__, 4, 'ENOTIMPLEMENTED',
+                              'Insertion of a range is not implemented yet.')
+            raise _RangeInsertionError()
+
     # Substitution.
     if variant.MutationType == 'subst':
         apply_substitution(first, argument, sequence, mutator, record, output)
diff --git a/tests/test_variantchecker.py b/tests/test_variantchecker.py
index 1fba607f8811afb84ce1bb2b663a3b1fc7071f76..be4c39bf5e585aa445850091e5f7e2cd5ba84dba 100644
--- a/tests/test_variantchecker.py
+++ b/tests/test_variantchecker.py
@@ -337,3 +337,17 @@ class TestVariantchecker():
         # Todo: For now, the following is how to check if protein
         # prediction is done.
         assert self.output.getOutput('newprotein')
+
+    def test_ins_range(self):
+        """
+        Insertion of a range is not implemented yet.
+        """
+        check_variant('AB026906.1:c.274_275ins262_268', self.config, self.output)
+        assert_equal(len(self.output.getMessagesWithErrorCode('ENOTIMPLEMENTED')), 1)
+
+    def test_delins_range(self):
+        """
+        Deletion/insertion of a range is not implemented yet.
+        """
+        check_variant('AB026906.1:c.274delins262_268', self.config, self.output)
+        assert_equal(len(self.output.getMessagesWithErrorCode('ENOTIMPLEMENTED')), 1)