diff --git a/src/NzbDrone.Core/CustomFormats/Specifications/SizeSpecification.cs b/src/NzbDrone.Core/CustomFormats/Specifications/SizeSpecification.cs
index fe873f9ec..9e2fe766e 100644
--- a/src/NzbDrone.Core/CustomFormats/Specifications/SizeSpecification.cs
+++ b/src/NzbDrone.Core/CustomFormats/Specifications/SizeSpecification.cs
@@ -11,6 +11,7 @@ namespace NzbDrone.Core.CustomFormats
         {
             RuleFor(c => c.Min).GreaterThanOrEqualTo(0);
             RuleFor(c => c.Max).GreaterThan(c => c.Min);
+            RuleFor(c => c.Max).LessThanOrEqualTo(double.MaxValue);
         }
     }