diff --git a/prometheus_client/exposition.py b/prometheus_client/exposition.py
index 345b247d..c676d51c 100644
--- a/prometheus_client/exposition.py
+++ b/prometheus_client/exposition.py
@@ -198,6 +198,7 @@ def sample_line(line):
         try:
             mname = metric.name
             mtype = metric.type
+
             # Munging from OpenMetrics into Prometheus format.
             if mtype == 'counter':
                 mname = mname + '_total'
@@ -212,7 +213,7 @@ def sample_line(line):
                 mtype = 'histogram'
             elif mtype == 'unknown':
                 mtype = 'untyped'
-
+            
             output.append('# HELP {} {}\n'.format(
                 mname, metric.documentation.replace('\\', r'\\').replace('\n', r'\n')))
             output.append(f'# TYPE {mname} {mtype}\n')
diff --git a/prometheus_client/metrics_core.py b/prometheus_client/metrics_core.py
index 77b3e446..f1af4cfa 100644
--- a/prometheus_client/metrics_core.py
+++ b/prometheus_client/metrics_core.py
@@ -121,10 +121,12 @@ def __init__(self,
         if name.endswith('_total'):
             name = name[:-6]
         Metric.__init__(self, name, documentation, 'counter', unit)
-        if labels is not None and value is not None:
-            raise ValueError('Can only specify at most one of value and labels.')
+
         if labels is None:
             labels = []
+        elif value is not None:
+            raise ValueError('Can only specify at most one of value and labels.')
+
         self._labelnames = tuple(labels)
         if value is not None:
             self.add_metric([], value, created)
@@ -196,10 +198,12 @@ def __init__(self,
         Metric.__init__(self, name, documentation, 'summary', unit)
         if (sum_value is None) != (count_value is None):
             raise ValueError('count_value and sum_value must be provided together.')
-        if labels is not None and count_value is not None:
-            raise ValueError('Can only specify at most one of value and labels.')
-        if labels is None:
+
+        if (labels is None):
             labels = []
+        elif count_value is not None:
+            raise ValueError('Can only specify at most one of value and labels.')
+
         self._labelnames = tuple(labels)
         # The and clause is necessary only for typing, the above ValueError will raise if only one is set.
         if count_value is not None and sum_value is not None:
@@ -238,12 +242,15 @@ def __init__(self,
                  unit: str = '',
                  ):
         Metric.__init__(self, name, documentation, 'histogram', unit)
+
         if sum_value is not None and buckets is None:
             raise ValueError('sum value cannot be provided without buckets.')
-        if labels is not None and buckets is not None:
-            raise ValueError('Can only specify at most one of buckets and labels.')
+
         if labels is None:
             labels = []
+        elif buckets is not None:
+            raise ValueError('Can only specify at most one of buckets and labels.')
+
         self._labelnames = tuple(labels)
         if buckets is not None:
             self.add_metric([], buckets, sum_value)
diff --git a/prometheus_client/registry.py b/prometheus_client/registry.py
index 694e4bd8..e580f86e 100644
--- a/prometheus_client/registry.py
+++ b/prometheus_client/registry.py
@@ -63,10 +63,9 @@ def _get_names(self, collector):
         except AttributeError:
             pass
         # Otherwise, if auto describe is enabled use the collect function.
-        if not desc_func and self._auto_describe:
-            desc_func = collector.collect
-
         if not desc_func:
+            if self._auto_describe:
+                desc_func = collector.collect
             return []
 
         result = []