diff --git a/src/BenchmarkDotNet/Extensions/ProcessExtensions.cs b/src/BenchmarkDotNet/Extensions/ProcessExtensions.cs
index 0f5f2e5c5f..32ab982cd7 100644
--- a/src/BenchmarkDotNet/Extensions/ProcessExtensions.cs
+++ b/src/BenchmarkDotNet/Extensions/ProcessExtensions.cs
@@ -45,7 +45,8 @@ internal static string ToPresentation(this IntPtr processorAffinity, int process
 
         private static IntPtr FixAffinity(IntPtr processorAffinity)
         {
-            int cpuMask = (1 << Environment.ProcessorCount) - 1;
+            // Max supported affinity without CPU groups is 64
+            long cpuMask = Environment.ProcessorCount >= 64 ? unchecked((long)0xFFFF_FFFF_FFFF_FFFF) : (1L << Environment.ProcessorCount) - 1;
 
             return RuntimeInformation.Is64BitPlatform()
                 ? new IntPtr(processorAffinity.ToInt64() & cpuMask)
diff --git a/tests/BenchmarkDotNet.IntegrationTests/ProcessPropertiesTests.cs b/tests/BenchmarkDotNet.IntegrationTests/ProcessPropertiesTests.cs
index a03194dc6f..82eeb073b4 100644
--- a/tests/BenchmarkDotNet.IntegrationTests/ProcessPropertiesTests.cs
+++ b/tests/BenchmarkDotNet.IntegrationTests/ProcessPropertiesTests.cs
@@ -60,7 +60,7 @@ public void Ensure()
             {
                 if (Process.GetCurrentProcess().ProcessorAffinity != Value)
                 {
-                    throw new InvalidOperationException("Did not set custom affinity");
+                    throw new InvalidOperationException($"Did not set custom affinity {Process.GetCurrentProcess().ProcessorAffinity} != {Value}");
                 }
             }
         }