diff --git a/Modules/ModuleFactory.cs b/Modules/ModuleFactory.cs
index 13ea7b3..ed71320 100644
--- a/Modules/ModuleFactory.cs
+++ b/Modules/ModuleFactory.cs
@@ -21,7 +21,7 @@ public static class ModuleFactory
 
         public static IEnumerable<IQcModule> Create(CliOptions settings)
         {
-            if (settings.ModuleNames.First() == "all")
+            if (settings.ModuleNames.Any() == false || settings.ModuleNames.First() == "all")
             {
                 settings.ModuleNames = moduleMap.Keys;
                 return moduleMap.Values;
diff --git a/Utils/CliOptions.cs b/Utils/CliOptions.cs
index a4b4a29..a5639c2 100644
--- a/Utils/CliOptions.cs
+++ b/Utils/CliOptions.cs
@@ -24,8 +24,8 @@ public class CliOptions
         [Option('f', "format", Required = true, HelpText = "Type of input file.")]
         public ReaderType Format { get; set; }
 
-        [Option('m', "modules", Required = true, Min = 1, HelpText = "Space-separated list of modules to run, or 'all'.")]
-        public IEnumerable<string> ModuleNames { get; set; } = Array.Empty<string>();
+        [Option('m', "modules", Required = false, HelpText = "Space-separated list of modules to run, or 'all'.")]
+        public IEnumerable<string> ModuleNames { get; set; }
 
         public static CliOptions Settings { get; set; } = null!;