diff --git a/homeassistant/util/__init__.py b/homeassistant/util/__init__.py
index ad4ca18e4fe..281a7d5308c 100644
--- a/homeassistant/util/__init__.py
+++ b/homeassistant/util/__init__.py
@@ -87,7 +87,10 @@ def sanitize_path(path: str) -> str:
 
 def slugify(text: str, *, separator: str = "_") -> str:
     """Slugify a given text."""
-    return unicode_slug.slugify(text, separator=separator)
+    if text == "":
+        return ""
+    slug = unicode_slug.slugify(text, separator=separator)
+    return "unknown" if slug == "" else slug
 
 
 def repr_helper(inp: Any) -> str:
diff --git a/tests/util/test_init.py b/tests/util/test_init.py
index 3855b62deb6..34e95013b26 100644
--- a/tests/util/test_init.py
+++ b/tests/util/test_init.py
@@ -68,6 +68,12 @@ def test_slugify():
     assert util.slugify("Tèst_äöüß_ÄÖÜ") == "test_aouss_aou"
     assert util.slugify("影師嗎") == "ying_shi_ma"
     assert util.slugify("けいふぉんと") == "keihuonto"
+    assert util.slugify("$") == "unknown"
+    assert util.slugify("Ⓐ") == "unknown"
+    assert util.slugify("ⓑ") == "unknown"
+    assert util.slugify("$$$") == "unknown"
+    assert util.slugify("$something") == "something"
+    assert util.slugify("") == ""
 
 
 def test_repr_helper():