diff --git a/Sources/MMIOMacros/SwiftSyntaxExtensions/ArgumentParsing/ParsableMacro.swift b/Sources/MMIOMacros/SwiftSyntaxExtensions/ArgumentParsing/ParsableMacro.swift
index bb09cf8a..41f2005d 100644
--- a/Sources/MMIOMacros/SwiftSyntaxExtensions/ArgumentParsing/ParsableMacro.swift
+++ b/Sources/MMIOMacros/SwiftSyntaxExtensions/ArgumentParsing/ParsableMacro.swift
@@ -49,11 +49,11 @@ extension ParsableMacro {
     var attributeWithPlaceholders = AttributeSyntax(
       atSign: .atSignToken(),
       attributeName: TypeSyntax(stringLiteral: baseName))
-    var arguments: LabeledExprListSyntax? = nil
+    var arguments = LabeledExprListSyntax()
 
     for child in Mirror(reflecting: Self()).children {
       guard let child = child.value as? any ArgumentProtocol else { continue }
-      if arguments == nil {
+      if arguments.isEmpty {
         signature += "("
         attributeWithPlaceholders.leftParen = .leftParenToken()
         arguments = .init()
@@ -67,10 +67,15 @@ extension ParsableMacro {
         expression: EditorPlaceholderExprSyntax(
           placeholder: .identifier("<#\(child.typePlaceholder)#>")))
 
-      arguments?.append(argument)
+      if !arguments.isEmpty {
+        let lastIndex = arguments.index(before: arguments.endIndex)
+        arguments[lastIndex].trailingComma = .commaToken(trailingTrivia: .space)
+      }
+
+      arguments.append(argument)
     }
 
-    if let arguments = arguments {
+    if !arguments.isEmpty {
       signature += ")"
       attributeWithPlaceholders.arguments = .argumentList(arguments)
       attributeWithPlaceholders.rightParen = .rightParenToken()
diff --git a/Tests/MMIOMacrosTests/SwiftSyntaxExtensions/ArgumentParsingTests/ArgumentParsing/ParsableMacroTests.swift b/Tests/MMIOMacrosTests/SwiftSyntaxExtensions/ArgumentParsingTests/ArgumentParsing/ParsableMacroTests.swift
index 664c8339..08fe54fb 100644
--- a/Tests/MMIOMacrosTests/SwiftSyntaxExtensions/ArgumentParsingTests/ArgumentParsing/ParsableMacroTests.swift
+++ b/Tests/MMIOMacrosTests/SwiftSyntaxExtensions/ArgumentParsingTests/ArgumentParsing/ParsableMacroTests.swift
@@ -19,24 +19,25 @@ import XCTest
 protocol MMIOArgumentParsingMacro: MMIOMemberMacro {}
 extension MMIOArgumentParsingMacro {
   static var memberMacroSuppressParsingDiagnostics: Bool { false }
+
   mutating func expansion(
     of node: AttributeSyntax,
     providingMembersOf declaration: some DeclGroupSyntax,
     in context: MacroContext<Self, some MacroExpansionContext>
   ) throws -> [DeclSyntax] { [] }
+
+  mutating func update(
+    label: String,
+    from expression: ExprSyntax,
+    in context: MacroContext<some ParsableMacro, some MacroExpansionContext>
+  ) throws {
+    fatalError()
+  }
 }
 
 final class ParsableMacroTests: XCTestCase {
   func test_noArguments_parse() {
-    struct A: MMIOArgumentParsingMacro {
-      mutating func update(
-        label: String,
-        from expression: ExprSyntax,
-        in context: MacroContext<some ParsableMacro, some MacroExpansionContext>
-      ) throws {
-        fatalError()
-      }
-    }
+    struct A: MMIOArgumentParsingMacro {}
 
     // Good...
     assertMacroExpansion(
@@ -526,4 +527,45 @@ final class ParsableMacroTests: XCTestCase {
       ],
       macros: ["A": A.self])
   }
+
+  func test_many_signatures() {
+    struct A: MMIOArgumentParsingMacro {}
+    struct B: MMIOArgumentParsingMacro {
+      @Argument(label: "foo")
+      var foo: Int
+    }
+    struct C: MMIOArgumentParsingMacro {
+      @Argument(label: "foo")
+      var foo: Int
+
+      @Argument(label: "bar")
+      var bar: Int
+    }
+    struct D: MMIOArgumentParsingMacro {
+      @Argument(label: "foo")
+      var foo: Int
+    }
+    struct E: MMIOArgumentParsingMacro {
+      @Argument(label: "foo")
+      var foo: Int?
+    }
+    struct F: MMIOArgumentParsingMacro {
+      @Argument(label: "foo")
+      var foo: [Int]
+    }
+
+    XCTAssertEqual(A.signature, "@A")
+    XCTAssertEqual(B.signature, "@B(foo:)")
+    XCTAssertEqual(C.signature, "@C(foo:bar:)")
+    XCTAssertEqual(D.signature, "@D(foo:)")
+    XCTAssertEqual(E.signature, "@E(foo:)")
+    XCTAssertEqual(F.signature, "@F(foo:)")
+
+    XCTAssertEqual("\(A.attributeWithPlaceholders)", "@A")
+    XCTAssertEqual("\(B.attributeWithPlaceholders)", "@B(foo: <#Int#>)")
+    XCTAssertEqual("\(C.attributeWithPlaceholders)", "@C(foo: <#Int#>, bar: <#Int#>)")
+    XCTAssertEqual("\(D.attributeWithPlaceholders)", "@D(foo: <#Int#>)")
+    XCTAssertEqual("\(E.attributeWithPlaceholders)", "@E(foo: <#Int#>)")
+    XCTAssertEqual("\(F.attributeWithPlaceholders)", "@F(foo: <#Int#>)")
+  }
 }