diff --git a/src/CommandLineUtils/Conventions/OptionAttributeConventionBase.cs b/src/CommandLineUtils/Conventions/OptionAttributeConventionBase.cs
index 36fa7cea..fe9446ab 100644
--- a/src/CommandLineUtils/Conventions/OptionAttributeConventionBase.cs
+++ b/src/CommandLineUtils/Conventions/OptionAttributeConventionBase.cs
@@ -81,11 +81,16 @@ private protected void AddOption(ConventionContext context, CommandOption option
                             {
                                 if (getter.Invoke(modelAccessor.GetModel()) is IEnumerable<object> values)
                                 {
+                                    var count = 0;
                                     foreach (var value in values)
                                     {
+                                        count++;
                                         option.TryParse(value?.ToString());
                                     }
-                                    option.DefaultValue = string.Join(", ", values.Select(x => x?.ToString()));
+                                    if (count > 0)
+                                    {
+                                        option.DefaultValue = string.Join(", ", values.Select(x => x?.ToString()));
+                                    }
                                 }
                             }
                         }
diff --git a/test/CommandLineUtils.Tests/FilePathExistsAttributeTests.cs b/test/CommandLineUtils.Tests/FilePathExistsAttributeTests.cs
index 2a4c0197..c561c38c 100644
--- a/test/CommandLineUtils.Tests/FilePathExistsAttributeTests.cs
+++ b/test/CommandLineUtils.Tests/FilePathExistsAttributeTests.cs
@@ -174,5 +174,32 @@ public void ValidatesOnlyFiles()
             Assert.Equal(0, CommandLineApplication.Execute<OnlyFile>(context));
             Assert.NotEqual(0, CommandLineApplication.Execute<OnlyDir>(context));
         }
+
+        private class OptionalFileChecks
+        {
+            [DirectoryExists]
+            [Option]
+            public string[] Dir { get; } = new string[0];
+
+            [FileExists]
+            [Option]
+            public string? File { get; }
+
+            private void OnExecute() { }
+        }
+
+        [Theory]
+        [InlineData(0, new string[0])]
+        [InlineData(1, new[] { "-f", "file.txt" })]
+        [InlineData(1, new[] { "-d", "dir1" })]
+        public void OnlyValidatesOptionsIfSpecified(int exitCode, string[] args)
+        {
+            var context = new DefaultCommandLineContext(
+                new TestConsole(_output),
+                AppContext.BaseDirectory,
+                args);
+
+            Assert.Equal(exitCode, CommandLineApplication.Execute<OptionalFileChecks>(context));
+        }
     }
 }
diff --git a/test/CommandLineUtils.Tests/OptionAttributeTests.cs b/test/CommandLineUtils.Tests/OptionAttributeTests.cs
index 8214d0f9..f15def5b 100644
--- a/test/CommandLineUtils.Tests/OptionAttributeTests.cs
+++ b/test/CommandLineUtils.Tests/OptionAttributeTests.cs
@@ -151,35 +151,79 @@ private class OptionHasDefaultValues
 
             [Option("-a4")]
             public (bool hasValue, string value) Arg4 { get; } = (false, "Yellow");
+
+            [Option("-a5")]
+            public string[] Arg5 { get; } = new string[0];
         }
 
         [Fact]
         public void KeepsDefaultValues()
         {
-            var app1 = Create<OptionHasDefaultValues>();
-            app1.Parse("-a1", "z", "-a2", "y");
-            Assert.Equal("z", app1.Model.Arg1);
-            Assert.Equal(new[] { "y" }, app1.Model.Arg2);
-
-            var app2 = Create<OptionHasDefaultValues>();
-            app2.Parse("-a1", "z");
-            Assert.Equal("z", app2.Model.Arg1);
-            Assert.Equal(new[] { "b", "c" }, app2.Model.Arg2);
-
-            var app3 = Create<OptionHasDefaultValues>();
-            app3.Parse();
-            Assert.Equal("a", app3.Model.Arg1);
-            Assert.Equal(new[] { "b", "c" }, app3.Model.Arg2);
-            Assert.False(app3.Model.Arg3.HasValue, "Should not have value");
-            Assert.False(app3.Model.Arg4.hasValue, "Should not have value");
-            Assert.Equal((false, "Yellow"), app3.Model.Arg4);
-
-            var app4 = Create<OptionHasDefaultValues>();
-            app4.Parse("-a3", "-a4");
-            Assert.True(app4.Model.Arg3.HasValue);
-            Assert.True(app4.Model.Arg4.hasValue);
-            Assert.True(app4.Model.Arg3);
-            Assert.Equal((true, null), app4.Model.Arg4);
+            {
+                var app1 = Create<OptionHasDefaultValues>();
+                app1.Parse("-a1", "z", "-a2", "y");
+                Assert.Equal("z", app1.Model.Arg1);
+                Assert.Equal(new[] { "y" }, app1.Model.Arg2);
+            }
+
+            {
+                var app2 = Create<OptionHasDefaultValues>();
+                app2.Parse("-a1", "z");
+                Assert.Equal("z", app2.Model.Arg1);
+                Assert.Equal(new[] { "b", "c" }, app2.Model.Arg2);
+            }
+            {
+                var app3 = Create<OptionHasDefaultValues>();
+                app3.Parse();
+                Assert.Equal("a", app3.Model.Arg1);
+                Assert.Equal(new[] { "b", "c" }, app3.Model.Arg2);
+                Assert.False(app3.Model.Arg3.HasValue, "Should not have value");
+                Assert.False(app3.Model.Arg4.hasValue, "Should not have value");
+                Assert.Equal((false, "Yellow"), app3.Model.Arg4);
+                Assert.Equal(Array.Empty<string>(), app3.Model.Arg5);
+            }
+
+            {
+                var app4 = Create<OptionHasDefaultValues>();
+                app4.Parse("-a3", "-a4");
+                Assert.True(app4.Model.Arg3.HasValue);
+                Assert.True(app4.Model.Arg4.hasValue);
+                Assert.True(app4.Model.Arg3);
+                Assert.Equal((true, null), app4.Model.Arg4);
+                Assert.Equal(Array.Empty<string>(), app4.Model.Arg5);
+            }
+
+            {
+                var app5 = Create<OptionHasDefaultValues>();
+                app5.Parse("-a5", "a", "-a5", "b");
+                Assert.Equal(new[] { "a", "b" }, app5.Model.Arg5);
+            }
+        }
+
+        private class AppWithMultiValueStringOption
+        {
+            [Option("-o1")]
+            string[] Opt1 { get; }
+
+            [Option("-o2")]
+            string[] Opt2 { get; } = new string[0];
+        }
+
+        [Fact]
+        public void SetsDefaultValueRightForStringArrayOptions()
+        {
+            var app = Create<AppWithMultiValueStringOption>();
+            app.Parse();
+            {
+                var opt1 = app.GetOptions().Single(o => o.ShortName == "o1");
+                Assert.Null(opt1.DefaultValue);
+                Assert.Empty(opt1.Values);
+            }
+            {
+                var opt2 = app.GetOptions().Single(o => o.ShortName == "o2");
+                Assert.Null(opt2.DefaultValue);
+                Assert.Empty(opt2.Values);
+            }
         }
 
         private class PrivateSetterProgram