diff --git a/tests/test_temperature.py b/tests/test_temperature.py
index 45f3c94b7..03fbb1ab4 100644
--- a/tests/test_temperature.py
+++ b/tests/test_temperature.py
@@ -889,6 +889,32 @@ def test_nan_presence(self, tasmax_series):
         np.testing.assert_array_equal(hwi, [np.nan])
 
 
+class TestHeatWaveMagnitude:
+    def test_simple(self, tasmax_series):
+        tx = np.zeros(366)
+        tx[:5] = np.array([30, 30, 30, 30, 30])
+        tx = tasmax_series(tx + K2C, start="1/1/2000")
+        hwm = atmos.heat_wave_magnitude(tx, freq="YS")
+        np.testing.assert_array_equal(hwm, [25])
+
+    def test_convert_units(self, tasmax_series):
+        tx = np.zeros(366)
+        tx[:5] = np.array([30, 30, 30, 30, 30])
+        tx = tasmax_series(tx, start="1/1/2000")
+        tx.attrs["units"] = "C"
+        hwm = atmos.heat_wave_magnitude(tx, freq="YS")
+        np.testing.assert_array_equal(hwm, [25])
+
+    def test_nan_presence(self, tasmax_series):
+        tx = np.zeros(366)
+        tx[:5] = np.array([30, 30, 30, 30, 30])
+        tx[-1] = np.nan
+        tx = tasmax_series(tx + K2C, start="1/1/2000")
+
+        hwm = atmos.heat_wave_magnitude(tx, freq="YS")
+        np.testing.assert_array_equal(hwm, [np.nan])
+
+
 class TestDailyFreezeThaw:
     nc_tasmax = os.path.join("NRCANdaily", "nrcan_canada_daily_tasmax_1990.nc")
     nc_tasmin = os.path.join("NRCANdaily", "nrcan_canada_daily_tasmin_1990.nc")
diff --git a/xclim/indicators/atmos/_temperature.py b/xclim/indicators/atmos/_temperature.py
index e13f82e07..df540d697 100644
--- a/xclim/indicators/atmos/_temperature.py
+++ b/xclim/indicators/atmos/_temperature.py
@@ -220,11 +220,11 @@ class TempWithIndexing(ResamplingIndicatorWithIndexing):
     title="Heat wave magnitude",
     identifier="heat_wave_magnitude",
     units="degC",
-    long_name="Maximum difference between daily maximum temperature and {thresh_tasmax} for days within a heat wave. "
+    long_name="Maximum difference between daily maximum temperature and {thresh} for days within a heat wave. "
     "A heat wave is defined as a series of at least {window} consecutive days with daily maximum temperature above "
-    "{thresh_tasmax}.",
+    "{thresh}.",
     description="Magnitude of the most intensive heat wave per {freq} as accumulated deg C above a given threshold "
-    "A heat wave occurs when daily maximum temperatures exceed {thresh_tasmax} for {window} days.",
+    "A heat wave occurs when daily maximum temperatures exceed {thresh} for {window} days.",
     abstract="Magnitude of the most intensive heat wave per {freq}. A heat wave occurs when daily maximum "
     "temperatures exceed given thresholds for a number of days.",
     cell_methods="",
diff --git a/xclim/indices/_threshold.py b/xclim/indices/_threshold.py
index e3e8b1097..ac8add779 100644
--- a/xclim/indices/_threshold.py
+++ b/xclim/indices/_threshold.py
@@ -1974,7 +1974,7 @@ def heat_wave_magnitude(
     out = rl.resample_and_rl(
         over_values,
         resample_before_rl,
-        rl.windowed_run_sum,
+        rl.windowed_max_run_sum,
         window=window,
         freq=freq,
     )