diff --git a/History b/History
index 7a957465..2c7d57cb 100644
--- a/History
+++ b/History
@@ -1,3 +1,5 @@
+* 8.2.1
+- Fix occasional "Collection was modified" exception when serializing metrics. #464
 * 8.2.0
 - .WithLabels() & similar now accept ReadOnlyMemory<string> as alternative to string[]. Same behavior, just easier to use if you already have a ReadOnlyMemory<string>.
 - .WithLabels() & similar now accept ReadOnlySpan<string> as alternative to string[]. This enables allocation-free metric instance creation if a metric instance with these labels is already known.
diff --git a/Prometheus/CollectorRegistry.cs b/Prometheus/CollectorRegistry.cs
index 78d01e71..35f1971c 100644
--- a/Prometheus/CollectorRegistry.cs
+++ b/Prometheus/CollectorRegistry.cs
@@ -386,33 +386,59 @@ private void UpdateRegistryMetrics()
         if (_metricFamiliesPerType == null || _metricInstancesPerType == null || _metricTimeseriesPerType == null)
             return; // Debug metrics are not enabled.
 
-        foreach (MetricType type in Enum.GetValues(typeof(MetricType)))
+        // We copy references to the metric families to a temporary buffer to avoid having to hold locks to keep the collection consistent.
+        CollectorFamily[] familiesBuffer;
+
+        _familiesLock.EnterReadLock();
+
+        var familiesCount = _families.Count;
+        familiesBuffer = ArrayPool<CollectorFamily>.Shared.Rent(familiesCount);
+
+        try
         {
-            long families = 0;
-            long instances = 0;
-            long timeseries = 0;
+            try
+            {
+                _families.Values.CopyTo(familiesBuffer, 0);
+            }
+            finally
+            {
+                _familiesLock.ExitReadLock();
+            }
 
-            foreach (var family in _families.Values)
+            foreach (MetricType type in Enum.GetValues(typeof(MetricType)))
             {
-                bool hadMatchingType = false;
+                long families = 0;
+                long instances = 0;
+                long timeseries = 0;
 
-                family.ForEachCollector(collector =>
+                for (var i = 0; i < familiesCount; i++)
                 {
-                    if (collector.Type != type)
-                        return;
+                    var family = familiesBuffer[i];
 
-                    hadMatchingType = true;
-                    instances += collector.ChildCount;
-                    timeseries += collector.TimeseriesCount;
-                });
+                    bool hadMatchingType = false;
 
-                if (hadMatchingType)
-                    families++;
-            }
+                    family.ForEachCollector(collector =>
+                    {
+                        if (collector.Type != type)
+                            return;
+
+                        hadMatchingType = true;
+                        instances += collector.ChildCount;
+                        timeseries += collector.TimeseriesCount;
+                    });
 
-            _metricFamiliesPerType[type].Set(families);
-            _metricInstancesPerType[type].Set(instances);
-            _metricTimeseriesPerType[type].Set(timeseries);
+                    if (hadMatchingType)
+                        families++;
+                }
+
+                _metricFamiliesPerType[type].Set(families);
+                _metricInstancesPerType[type].Set(instances);
+                _metricTimeseriesPerType[type].Set(timeseries);
+            }
+        }
+        finally
+        {
+            ArrayPool<CollectorFamily>.Shared.Return(familiesBuffer, clearArray: true);
         }
     }
 
diff --git a/Resources/SolutionAssemblyInfo.cs b/Resources/SolutionAssemblyInfo.cs
index 2ec83a8b..1f300ba8 100644
--- a/Resources/SolutionAssemblyInfo.cs
+++ b/Resources/SolutionAssemblyInfo.cs
@@ -2,7 +2,7 @@
 using System.Runtime.CompilerServices;
 
 // This is the real version number, used in NuGet packages and for display purposes.
-[assembly: AssemblyFileVersion("8.2.0")]
+[assembly: AssemblyFileVersion("8.2.1")]
 
 // Only use major version here, with others kept at zero, for correct assembly binding logic.
 [assembly: AssemblyVersion("8.0.0")]
diff --git a/Sample.Console.DotNetMeters/CustomDotNetMeters.cs b/Sample.Console.DotNetMeters/CustomDotNetMeters.cs
index 9ec01552..296c9d36 100644
--- a/Sample.Console.DotNetMeters/CustomDotNetMeters.cs
+++ b/Sample.Console.DotNetMeters/CustomDotNetMeters.cs
@@ -65,7 +65,8 @@ int MeasureSandLevel()
                 if (Random.Shared.Next(10) == 0)
                     counter1.Add(1, new KeyValuePair<string, object?>("wing-type", "SlaxxWing 1.0"), new KeyValuePair<string, object?>("wing-version", "beta"));
 
-                histogram1.Record((byte)(Random.Shared.Next(256)), new KeyValuePair<string, object?>("is-faulted", true));
+                // is-faulted here conflicts with the static label of the same name and gets overwritten by the static label.
+                histogram1.Record((byte)(Random.Shared.Next(256)), new KeyValuePair<string, object?>("is-faulted", true), new KeyValuePair<string, object?>("canbus_ver", "1.0"));
 
                 // .NET 7
                 upDown1.Add(Random.Shared.Next(-1, 2));