diff --git a/send2trash/plat_other.py b/send2trash/plat_other.py
index 6f80275..9c774e4 100644
--- a/send2trash/plat_other.py
+++ b/send2trash/plat_other.py
@@ -46,6 +46,9 @@ def is_parent(parent, path):
     parent = op.realpath(parent)
     if isinstance(parent, str):
         parent = os.fsencode(parent)
+    # Ensure parent ends with a separator to prevent invalid substring matches
+    if not parent.endswith(b"/"):
+        parent += b"/"
     return path.startswith(parent)
 
 
diff --git a/tests/test_plat_other.py b/tests/test_plat_other.py
index e451175..ea69673 100644
--- a/tests/test_plat_other.py
+++ b/tests/test_plat_other.py
@@ -99,7 +99,12 @@ class ExtVol:
 
         def s_getdev(path):
             st = os.lstat(path)
-            if is_parent(self.trash_topdir, path):
+            path_real = op.realpath(path)
+            if isinstance(path_real, bytes):
+                topdir_real = os.fsencode(op.realpath(self.trash_topdir))
+            else:
+                topdir_real = op.realpath(self.trash_topdir)
+            if path_real == topdir_real or is_parent(self.trash_topdir, path):
                 return "dev"
             return st.st_dev
 
@@ -207,3 +212,65 @@ def test_trash_symlink(gen_ext_vol):
         is True
     )
     os.remove(sl_dir)
+
+
+def test_is_parent_substring_path_bug_e2e():
+    """
+    End-to-end test that is_parent() substring bug doesn't affect trashing.
+
+    This test prevents a bug where paths like ~/.local/share (HOMETRASH) would be
+    incorrectly considered as the parent of ~/.local/shared due to simple substring
+    matching without checking for path separators. This would cause incorrect relative
+    path computation in the trash info file (should be absolute path since the file
+    is not actually under ~/.local/share).
+    """
+    # Create a sibling directory to HOMETRASH with a similar name
+    shared_dir = op.expanduser("~/.local/shared")
+    os.makedirs(shared_dir, exist_ok=True)
+
+    try:
+        # Create a test file in the shared directory
+        test_file = op.join(shared_dir, "test_substring_bug.txt")
+        touch(test_file)
+        assert op.exists(test_file) is True
+
+        # Trash the file
+        s2t(test_file)
+
+        # File should be removed from original location
+        assert op.exists(test_file) is False
+
+        # Find the trash info file for this test file
+        trash_info_dir = op.join(HOMETRASH, "info")
+        trash_info_files = [f for f in os.listdir(trash_info_dir) if "substring_bug" in f]
+        assert len(trash_info_files) > 0, "No trash info file found for test file"
+
+        # Read the trash info file and verify the path is absolute
+        info_file_path = op.join(trash_info_dir, trash_info_files[0])
+        cfg = ConfigParser()
+        cfg.read(info_file_path)
+        trashed_path = cfg.get("Trash Info", "Path", raw=True)
+
+        # The path should be absolute, not relative
+        # If the bug exists, it might be a relative path like "shared/test_substring_bug.txt"
+        # instead of the full absolute path
+        assert op.isabs(trashed_path) or trashed_path.startswith("/"), (
+            f"Path in trash info should be absolute, got: {trashed_path}. "
+            "This suggests is_parent() is incorrectly treating ~/.local/share as parent."
+        )
+
+    finally:
+        # Cleanup
+        if op.exists(shared_dir):
+            shutil.rmtree(shared_dir)
+        # Clean up any trash files created by this test
+        trash_files_dir = op.join(HOMETRASH, "files")
+        trash_info_dir = op.join(HOMETRASH, "info")
+        if op.exists(trash_files_dir):
+            for f in os.listdir(trash_files_dir):
+                if "substring_bug" in f:
+                    os.remove(op.join(trash_files_dir, f))
+        if op.exists(trash_info_dir):
+            for f in os.listdir(trash_info_dir):
+                if "substring_bug" in f:
+                    os.remove(op.join(trash_info_dir, f))