diff --git a/homeassistant/components/prometheus/__init__.py b/homeassistant/components/prometheus/__init__.py
index 71d56cda18a..c20296a2c18 100644
--- a/homeassistant/components/prometheus/__init__.py
+++ b/homeassistant/components/prometheus/__init__.py
@@ -168,7 +168,10 @@ class PrometheusMetrics:
         return "".join(
             [
                 c
-                if c in string.ascii_letters or c.isdigit() or c == "_" or c == ":"
+                if c in string.ascii_letters
+                or c in string.digits
+                or c == "_"
+                or c == ":"
                 else f"u{hex(ord(c))}"
                 for c in metric
             ]
diff --git a/tests/components/prometheus/test_init.py b/tests/components/prometheus/test_init.py
index 206d7477509..5c6189a811e 100644
--- a/tests/components/prometheus/test_init.py
+++ b/tests/components/prometheus/test_init.py
@@ -46,6 +46,13 @@ async def prometheus_client(loop, hass, hass_client):
     sensor4.entity_id = "sensor.wind_direction"
     await sensor4.async_update_ha_state()
 
+    sensor5 = DemoSensor(
+        None, "SPS30 PM <1µm Weight concentration", 3.7069, None, "µg/m³", None
+    )
+    sensor5.hass = hass
+    sensor5.entity_id = "sensor.sps30_pm_1um_weight_concentration"
+    await sensor5.async_update_ha_state()
+
     return await hass_client()
 
 
@@ -113,3 +120,9 @@ async def test_view(prometheus_client):  # pylint: disable=redefined-outer-name
         'entity="sensor.wind_direction",'
         'friendly_name="Wind Direction"} 25.0' in body
     )
+
+    assert (
+        'sensor_unit_u0xb5g_per_mu0xb3{domain="sensor",'
+        'entity="sensor.sps30_pm_1um_weight_concentration",'
+        'friendly_name="SPS30 PM <1µm Weight concentration"} 3.7069' in body
+    )