diff --git a/src/iris_grib/_load_convert.py b/src/iris_grib/_load_convert.py
index 1a055e15..d4003285 100644
--- a/src/iris_grib/_load_convert.py
+++ b/src/iris_grib/_load_convert.py
@@ -209,7 +209,7 @@ def _masker(item):
 # Non-standardised usage for negative forecast times.
 def _hindcast_fix(forecast_time):
     """Return a forecast time interpreted as a possibly negative value."""
-    uft = np.uint32(forecast_time)
+    uft = np.array(forecast_time).astype(np.uint32)
     HIGHBIT = 2**30
 
     # Workaround grib api's assumption that forecast time is positive.
diff --git a/src/iris_grib/message.py b/src/iris_grib/message.py
index aab46f81..9adcc3db 100644
--- a/src/iris_grib/message.py
+++ b/src/iris_grib/message.py
@@ -27,6 +27,8 @@
     "longitudes": "longitude",
     # Support older form of key which used to exist before eccodes 2v36
     "indicatorOfUnitForForecastTime": "indicatorOfUnitOfTimeRange",
+    # Support older name which became an alias at eccodes 2v38
+    "numberOfTimeRange": "numberOfTimeRanges",
 }