@@ -28,8 +28,12 @@ Unreleased
   ``else:`` body removes the ``else:`` line.  Previously the ``case`` line was
   left behind and reported as missing.  Closes `issue 1563`_ with `pull 2269`_.
 
+- Fix: using :meth:`.CoverageData.update` twice on an in-memory database would
+  fail, as described in `issue 2279`_. This is now fixed.
+
 .. _issue 1563: https://github.com/coveragepy/coveragepy/issues/1563
 .. _pull 2269: https://github.com/coveragepy/coveragepy/pull/2269
+.. _issue 2279: https://github.com/coveragepy/coveragepy/issues/2279
 
 .. start-releases
 
 
@@ -880,6 +880,13 @@ def map_with_fixed_slashes(p: str) -> str:
                 INNER JOIN main.file AS main_file ON other_file_mapped.mapped_path = main_file.path
             """)
 
+            # Clean up in case we'll use update() again.
+            con.execute_void("DROP TABLE other_file_mapped")
+            if has_arcs:
+                con.execute_void("DROP TABLE context_mapping")
+            con.con.commit()
+            con.execute_void("DETACH DATABASE other_db")
+
         if not self._no_disk:
             # Update all internal cache data.
             self._reset()
 
@@ -526,6 +526,24 @@ def test_update_arcs_empty(self) -> None:
         covdata1.update(covdata2)
         assert_line_counts(covdata1, SUMMARY_3)
 
+    def test_update_lines_in_memory_twice(self) -> None:
+        combined = DebugCoverageData(no_disk=True)
+        for index in range(2):
+            source = DebugCoverageData(no_disk=True)
+            source.add_lines({"example.py": {index + 1}})
+            source.write()
+            combined.update(source)
+        assert combined.lines("example.py") == [1, 2]
+
+    def test_update_arcs_in_memory_twice(self) -> None:
+        combined = DebugCoverageData(no_disk=True)
+        for index in range(2):
+            source = DebugCoverageData(no_disk=True)
+            source.add_arcs({"example.py": {(index + 1, 10)}})
+            source.write()
+            combined.update(source)
+        assert combined.arcs("example.py") == [(1, 10), (2, 10)]
+
     def test_asking_isnt_measuring(self) -> None:
         # Asking about an unmeasured file shouldn't make it seem measured.
         covdata = DebugCoverageData()