diff --git a/test/functional/tests/cache_ops/test_core_remove.py b/test/functional/tests/cache_ops/test_core_remove.py
index 1c6e57f..2f79e47 100644
--- a/test/functional/tests/cache_ops/test_core_remove.py
+++ b/test/functional/tests/cache_ops/test_core_remove.py
@@ -14,6 +14,7 @@ from test_utils.output import CmdException
 from test_utils.size import Size, Unit
 
 mount_point = "/mnt/cas"
+cores_amount = 3
 
 
 @pytest.mark.require_disk("cache", DiskTypeSet([DiskType.optane, DiskType.nand]))
@@ -54,3 +55,44 @@ def test_remove_core_when_other_mounted_auto_numeration():
         except CmdException as exc:
             TestRun.fail(f"Cannot remove the unmounted core.\n{exc}")
 
+
+@pytest.mark.require_disk("cache", DiskTypeSet([DiskType.optane, DiskType.nand]))
+@pytest.mark.require_disk("core", DiskTypeLowerThan("cache"))
+def test_remove_core_when_other_mounted_custom_numeration():
+    """
+        title: |
+          Test for removing one core from the cache when the other core is mounted.
+          Cores have custom numeration, starting with the same digit.
+        description: |
+          Test of the ability to remove the unmounted core from the cache when the other core
+          is mounted and its ID starts with the same digit.
+        pass_criteria:
+          - No system crash.
+          - Removing unmounted core finished with success.
+    """
+    with TestRun.step("Prepare devices."):
+        cache_device = TestRun.disks['cache']
+        cache_device.create_partitions([Size(50, Unit.MebiByte)])
+        cache_part = cache_device.partitions[0]
+        core_device = TestRun.disks['core']
+        core_device.create_partitions([Size(200, Unit.MebiByte)] * cores_amount)
+
+    with TestRun.step("Start cache."):
+        cache = casadm.start_cache(cache_part, force=True)
+
+    with TestRun.step("Add cores to cache and mount them except the first one."):
+        random_prefix = random.randint(1, 9)
+        random_interfix = random.randint(1, 9)
+
+        free_core = cache.add_core(core_device.partitions[0], random_prefix)
+        mounted_cores = []
+        for i, part in enumerate(core_device.partitions[1:]):
+            part.create_filesystem(Filesystem.xfs)
+            mounted_cores.append(cache.add_core(part, f"{random_prefix}{random_interfix}{i}"))
+            mounted_cores[i].mount(f"{mount_point}{cache.cache_id}-{mounted_cores[i].core_id}")
+
+    with TestRun.step("Remove the unmounted core."):
+        try:
+            cache.remove_core(free_core.core_id)
+        except CmdException as exc:
+            TestRun.fail(f"Cannot remove the unmounted core.\n{exc}")