diff --git a/Sources/ResgenSwift/Strings/Generator/StringsFileGenerator.swift b/Sources/ResgenSwift/Strings/Generator/StringsFileGenerator.swift
index e8c20fc..358a9bc 100644
--- a/Sources/ResgenSwift/Strings/Generator/StringsFileGenerator.swift
+++ b/Sources/ResgenSwift/Strings/Generator/StringsFileGenerator.swift
@@ -12,7 +12,12 @@ class StringsFileGenerator {
     
     // MARK: - Strings Files
     
-    static func writeStringsFiles(sections: [Section], langs: [String], defaultLang: String, tags: [String], outputPath: String, inputFilenameWithoutExt: String) {
+    static func writeStringsFiles(sections: [Section],
+                                  langs: [String],
+                                  defaultLang: String,
+                                  tags: [String],
+                                  outputPath: String,
+                                  inputFilenameWithoutExt: String) {
         var stringsFilesContent = [String: String]()
         for lang in langs {
             stringsFilesContent[lang] = Self.generateStringsFileContent(lang: lang,
@@ -37,7 +42,10 @@ class StringsFileGenerator {
         }
     }
     
-    static func generateStringsFileContent(lang: String, defaultLang: String, tags inputTags: [String], sections: [Section]) -> String {
+    static func generateStringsFileContent(lang: String,
+                                           defaultLang: String,
+                                           tags inputTags: [String],
+                                           sections: [Section]) -> String {
         var stringsFileContent = """
         /**
          * Apple Strings File
@@ -86,14 +94,22 @@ class StringsFileGenerator {
     
     // MARK: - Extension file
     
-    static func writeExtensionFiles(sections: [Section], defaultLang lang: String, tags: [String], staticVar: Bool, inputFilename: String, extensionName: String, extensionFilePath: String) {
+    static func writeExtensionFiles(sections: [Section],
+                                    defaultLang lang: String,
+                                    tags: [String],
+                                    staticVar: Bool,
+                                    inputFilename: String,
+                                    extensionName: String,
+                                    extensionFilePath: String,
+                                    extensionSuffix: String) {
         // Get extension content
         let extensionFileContent = Self.getExtensionContent(sections: sections,
                                                             defaultLang: lang,
                                                             tags: tags,
                                                             staticVar: staticVar,
                                                             inputFilename: inputFilename,
-                                                            extensionName: extensionName)
+                                                            extensionName: extensionName,
+                                                            extensionSuffix: extensionSuffix)
         
         // Write content
         let extensionFilePathURL = URL(fileURLWithPath: extensionFilePath)
@@ -108,10 +124,16 @@ class StringsFileGenerator {
     
     // MARK: - Extension content
     
-    static func getExtensionContent(sections: [Section], defaultLang lang: String, tags: [String], staticVar: Bool, inputFilename: String, extensionName: String) -> String {
+    static func getExtensionContent(sections: [Section],
+                                    defaultLang lang: String,
+                                    tags: [String],
+                                    staticVar: Bool,
+                                    inputFilename: String,
+                                    extensionName: String,
+                                    extensionSuffix: String) -> String {
         [
             Self.getHeader(stringsFilename: inputFilename, extensionClassname: extensionName),
-            Self.getEnumKey(sections: sections, tags: tags),
+            Self.getEnumKey(sections: sections, tags: tags, extensionSuffix: extensionSuffix),
             Self.getProperties(sections: sections, defaultLang: lang, tags: tags, staticVar: staticVar),
             Self.getFooter()
         ]
@@ -132,8 +154,8 @@ class StringsFileGenerator {
         """
     }
     
-    private static func getEnumKey(sections: [Section], tags: [String]) -> String {
-        var enumDefinition = "\n    enum Key: String {\n"
+    private static func getEnumKey(sections: [Section], tags: [String], extensionSuffix: String) -> String {
+        var enumDefinition = "\n    enum Key\(extensionSuffix.uppercasedFirst()): String {\n"
         
         sections.forEach { section in
             // Check that at least one string will be generated
diff --git a/Sources/ResgenSwift/Strings/Stringium/Stringium.swift b/Sources/ResgenSwift/Strings/Stringium/Stringium.swift
index d497e00..1e3897e 100644
--- a/Sources/ResgenSwift/Strings/Stringium/Stringium.swift
+++ b/Sources/ResgenSwift/Strings/Stringium/Stringium.swift
@@ -57,7 +57,8 @@ struct Stringium: ParsableCommand {
                                                  staticVar: options.staticMembers,
                                                  inputFilename: options.inputFilenameWithoutExt,
                                                  extensionName: options.extensionName,
-                                                 extensionFilePath: options.extensionFilePath)
+                                                 extensionFilePath: options.extensionFilePath,
+                                                 extensionSuffix: options.extensionSuffix)
         
         print("[\(Self.toolName)] Strings generated")
     }
diff --git a/Sources/ResgenSwift/Strings/Stringium/StringiumOptions.swift b/Sources/ResgenSwift/Strings/Stringium/StringiumOptions.swift
index 42549ba..1fd1d53 100644
--- a/Sources/ResgenSwift/Strings/Stringium/StringiumOptions.swift
+++ b/Sources/ResgenSwift/Strings/Stringium/StringiumOptions.swift
@@ -36,8 +36,8 @@ struct StringiumOptions: ParsableArguments {
     @Option(help: "Extension name. If not specified, it will generate an String extension.")
     var extensionName: String = Stringium.defaultExtensionName
     
-    @Option(help: "Extension suffix. Ex: MyApp, it will generate {extensionName}+{extensionSuffix}.swift")
-    var extensionSuffix: String?
+    @Option(help: "Extension suffix: {extensionName}+{extensionSuffix}.swift")
+    var extensionSuffix: String
 }
 
 // MARK: - Private var getter
@@ -68,10 +68,7 @@ extension StringiumOptions {
 
 extension StringiumOptions {
     var extensionFileName: String {
-        if let extensionSuffix = extensionSuffix {
-            return "\(extensionName)+\(extensionSuffix).swift"
-        }
-        return "\(extensionName).swift"
+        "\(extensionName)+\(extensionSuffix).swift"
     }
     
     var extensionFilePath: String {
diff --git a/Sources/ToolCore/StringExtensions.swift b/Sources/ToolCore/StringExtensions.swift
index 6d5077d..52ea186 100644
--- a/Sources/ToolCore/StringExtensions.swift
+++ b/Sources/ToolCore/StringExtensions.swift
@@ -85,4 +85,8 @@ public extension String {
         blue = String(colorClean.prefix(2))
         return (alpha: alpha, red: red, green: green, blue: blue)
     }
+    
+    func uppercasedFirst() -> String {
+        prefix(1).uppercased() + dropFirst()
+    }
 }
diff --git a/Tests/ResgenSwiftTests/Strings/StringsFileGeneratorTests.swift b/Tests/ResgenSwiftTests/Strings/StringsFileGeneratorTests.swift
index 5740bd5..5d3193c 100644
--- a/Tests/ResgenSwiftTests/Strings/StringsFileGeneratorTests.swift
+++ b/Tests/ResgenSwiftTests/Strings/StringsFileGeneratorTests.swift
@@ -131,7 +131,8 @@ final class StringsFileGeneratorTests: XCTestCase {
                                                                         tags: ["ios", "iosonly", "notranslation"],
                                                                         staticVar: false,
                                                                         inputFilename: "myInputFilename",
-                                                                        extensionName: "GenStrings")
+                                                                        extensionName: "GenStrings",
+                                                                        extensionSuffix: "strings")
         
         // Expect
         let expect = """
@@ -207,7 +208,8 @@ final class StringsFileGeneratorTests: XCTestCase {
                                                                         tags: ["ios", "iosonly", "notranslation"],
                                                                         staticVar: true,
                                                                         inputFilename: "myInputFilename",
-                                                                        extensionName: "GenStrings")
+                                                                        extensionName: "GenStrings",
+                                                                        extensionSuffix: "strings")
         
         // Expect
         let expect = """