diff --git a/goodwe_controller/DECISIONS/SAFETY-118-peak-forecast-unit.md b/goodwe_controller/DECISIONS/SAFETY-118-peak-forecast-unit.md
index aae71fd..37422d7 100644
--- a/goodwe_controller/DECISIONS/SAFETY-118-peak-forecast-unit.md
+++ b/goodwe_controller/DECISIONS/SAFETY-118-peak-forecast-unit.md
@@ -4,8 +4,8 @@
 
 `peak_forecast_entity` was read as a bare number, and anything under 50 was
 multiplied by 1000 ("accept kW or W"). A W sensor reading 17 to 45 W, which a
-real site did 430 times in one morning, was taken as 17 to 45 kW. The validator
-also called a kW sensor wrong, which was false for this entity.
+real site did 430 times in one morning, would be taken as 17 to 45 kW. The
+validator also called a kW sensor wrong, which was false for this entity.
 
 Decision: the size rule is gone. The entity is read through `pv.watts()`, the
 same unit table and reader as the solar entities, so W, kW, MW and the rest
diff --git a/goodwe_controller/app/main.py b/goodwe_controller/app/main.py
index ac6d57d..9e98549 100644
--- a/goodwe_controller/app/main.py
+++ b/goodwe_controller/app/main.py
@@ -3472,7 +3472,9 @@ class Controller:
             # power: not used, as if the option were empty.
             st = await self.hass.state(o["peak_forecast_entity"])
             self.peak_fc, _why = pv_read.watts(st)
-            self._peak_fc_unit_log(pv_read.unit_fault(st))
+            # A missing reading leaves the unit-fault state as it was.
+            if pv_read.has_reading(st):
+                self._peak_fc_unit_log(pv_read.unit_fault(st))
         else:
             self.peak_fc = None
             self._peak_fc_fault = None
diff --git a/goodwe_controller/app/pv.py b/goodwe_controller/app/pv.py
index fb70296..901e0c9 100644
--- a/goodwe_controller/app/pv.py
+++ b/goodwe_controller/app/pv.py
@@ -126,19 +126,26 @@ def watts(state: dict | None) -> tuple:
     return value * WATTS_PER[unit], unit
 
 
-def unit_fault(state: dict | None):
-    """SAFETY-118. `None` unless `state` holds a number whose unit cannot be
-    read in watts, then that unit (`""` for none). A missing, unavailable or
-    non-numeric state is a missing reading, not a unit fault, so it is `None`.
-    """
+def has_reading(state: dict | None) -> bool:
+    """SAFETY-118. True when `state` holds a number, so its unit can be judged.
+    A missing, unavailable, unknown or non-numeric state is a missing reading."""
     if state is None:
-        return None
+        return False
     raw = str(state.get("state", "")).strip()
     if raw.lower() in BAD_STATES:
-        return None
+        return False
     try:
         float(raw)
     except ValueError:
+        return False
+    return True
+
+
+def unit_fault(state: dict | None):
+    """SAFETY-118. `None` unless `state` holds a number whose unit cannot be
+    read in watts, then that unit (`""` for none). `None` also means a missing
+    reading: use `has_reading()` to tell it from a good unit."""
+    if not has_reading(state):
         return None
     unit = str((state.get("attributes") or {}).get(UNIT_KEY) or "").strip()
     return None if unit in WATTS_PER else unit
diff --git a/goodwe_controller/test_safety118.py b/goodwe_controller/test_safety118.py
index cc8319b..30058a6 100644
--- a/goodwe_controller/test_safety118.py
+++ b/goodwe_controller/test_safety118.py
@@ -178,15 +178,22 @@ check("no unit is a different cause and warns", len(warns()) == 3
       and "has no unit" in warns()[2])
 reads(c)
 check("...and only once", len(warns()) == 3)
+USED = (logging.INFO, "The 15-minute demand forecast is used again.")
+
+
+def used():
+    return [r for r in rec.rows if r == USED]
+
+
 h.fc = st("unavailable")
 reads(c)
-check("unavailable is no unit fault and adds no warning", len(warns()) == 3)
+check("unavailable adds no warning and no 'used again'",
+      len(warns()) == 3 and not used())
 h.fc = st(820, "W")
 reads(c)
-check("a good unit is read again and logs INFO, not a warning",
-      c.peak_fc == 820.0 and len(warns()) == 3
-      and rec.rows[-1] == (logging.INFO,
-                           "The 15-minute demand forecast is used again."))
+check("a good unit is read again: one INFO, no new warning",
+      c.peak_fc == 820.0 and len(warns()) == 3 and len(used()) == 1
+      and rec.rows[-1] == USED)
 n = len(warns())
 for s in (st(820, "W"), st(0.8, "kW")):
     h.fc = s
@@ -291,7 +298,72 @@ print("   NL bad unit:", messages.peak_forecast_unit("kWh", "nl"))
 check("the strings differ by cause and by language",
       len({messages.peak_forecast_unit(u, l) for u in ("", "kWh")
            for l in ("en", "nl")}) == 4)
-check("pv.unit_fault: None for a good unit and for a missing reading",
+print("6. a missing reading leaves the unit fault as it was (F1)")
+
+
+lg.addHandler(rec)
+
+
+def prow(c):
+    return [r for r in c.checks() if r.get("id") == "peak_forecast"]
+
+
+def flap(first, gap, last):
+    """first, gap, first again (or last): the log rows and the status row
+    after each cycle."""
+    rec.rows.clear()
+    c, h = make(first)
+    out = []
+    for s in (first, gap, last):
+        h.fc = s
+        reads(c)
+        out.append((len(warns()), len(used()), len(prow(c)), c.peak_fc))
+    return out
+
+
+for label, first, gap in [
+        ("kWh -> unavailable -> kWh", st(820, "kWh"), st("unavailable", "kWh")),
+        ("kWh -> unknown -> kWh", st(820, "kWh"), st("unknown", "kWh")),
+        ("kWh -> failed read -> kWh", st(820, "kWh"), None),
+        ("kWh -> non-numeric -> kWh", st(820, "kWh"), st("sunny", "kWh")),
+        ("no unit -> failed read -> no unit", st(820), None),
+        ("no unit -> unavailable -> no unit", st(820), st("unavailable"))]:
+    r = flap(first, gap, first)
+    check(f"{label}: one WARNING, no 'used again', row on all 3 ({r})",
+          [x[0] for x in r] == [1, 1, 1] and [x[1] for x in r] == [0, 0, 0]
+          and [x[2] for x in r] == [1, 1, 1]
+          and [x[3] for x in r] == [None, None, None])
+r = flap(st(820, "kWh"), st("unavailable", "kWh"), st(820, "W"))
+check(f"kWh -> unavailable -> W: the fault clears only on the W reading ({r})",
+      [x[1] for x in r] == [0, 0, 1] and [x[2] for x in r] == [1, 1, 0]
+      and [x[0] for x in r] == [1, 1, 1] and r[2][3] == 820.0)
+rec.rows.clear()
+c, h = make(st(820, "W"))
+for s in (st(820, "W"), st("unavailable", "W"), None, st("sunny", "W")):
+    h.fc = s
+    reads(c)
+    check(f"good unit, reading {s and s['state']!r}: no row, no log",
+          not prow(c) and not warns() and not used())
+rec.rows.clear()
+c, h = make(st(820, "kWh"))
+reads(c)
+for s in (st("unavailable", "kWh"), None):
+    h.fc = s
+    reads(c)
+    check("fault row stays while the reading is missing",
+          len(prow(c)) == 1 and prow(c)[0]["text"]
+          == messages.row_peak_forecast_unit("kWh"))
+c, h = make(st(820, "W"))
+h.fc = st("unavailable", "W")
+reads(c)
+check("good-unit sensor only unavailable: the fault row stays away",
+      not prow(c))
+lg.removeHandler(rec)
+check("has_reading: numbers only",
+      pv.has_reading(st(0, "kWh")) and pv.has_reading(st("1.5"))
+      and not pv.has_reading(None) and not pv.has_reading(st("unavailable"))
+      and not pv.has_reading(st("unknown")) and not pv.has_reading(st("x")))
+check("pv.unit_fault: None for a good unit and for a missing reading (has_reading tells them apart)",
       pv.unit_fault(st(1, "kW")) is None and pv.unit_fault(None) is None
       and pv.unit_fault(st("unavailable")) is None
       and pv.unit_fault(st(1)) == "" and pv.unit_fault(st(1, "kWh")) == "kWh")