diff --git a/Sources/OptionDescriptor.swift b/Sources/OptionDescriptor.swift
index a959c1e8..7349bf4f 100644
--- a/Sources/OptionDescriptor.swift
+++ b/Sources/OptionDescriptor.swift
@@ -101,9 +101,9 @@ class OptionDescriptor {
         type = .binary(true: trueValues, false: falseValues)
         toOptions = { value, options in
             switch value.lowercased() {
-            case let value where trueValues.contains(value):
+            case let value where trueValues.contains(where: { value == $0.lowercased() }):
                 options[keyPath: keyPath] = true
-            case let value where falseValues.contains(value):
+            case let value where falseValues.contains(where: { value == $0.lowercased() }):
                 options[keyPath: keyPath] = false
             default:
                 throw FormatError.options("")
diff --git a/Tests/OptionDescriptorTests.swift b/Tests/OptionDescriptorTests.swift
index a5a1b7c5..07719a38 100644
--- a/Tests/OptionDescriptorTests.swift
+++ b/Tests/OptionDescriptorTests.swift
@@ -349,4 +349,10 @@ class OptionDescriptorTests: XCTestCase {
         let options2 = FormatOptions(selfRequired: ["baz", "bar", "foo"])
         XCTAssertEqual(options1.description, options2.description)
     }
+
+    func testFileMacroCase() {
+        let argument = "#fileID"
+        var options: FormatOptions = .default
+        XCTAssertNoThrow(try Descriptors.preferFileMacro.toOptions(argument, &options))
+    }
 }