diff --git a/Sources/Splash/Grammar/SwiftGrammar.swift b/Sources/Splash/Grammar/SwiftGrammar.swift
index 79a98d5..3ffd142 100644
--- a/Sources/Splash/Grammar/SwiftGrammar.swift
+++ b/Sources/Splash/Grammar/SwiftGrammar.swift
@@ -13,13 +13,8 @@ public struct SwiftGrammar: Grammar {
     public var syntaxRules: [SyntaxRule]
 
     public init() {
-        var delimiters = CharacterSet.alphanumerics.inverted
-        delimiters.remove("_")
-        delimiters.remove("\"")
-        delimiters.remove("#")
-        delimiters.remove("@")
-        delimiters.remove("$")
-        self.delimiters = delimiters
+        let notDelimiters = CharacterSet(charactersIn: "_\"#@$")
+        self.delimiters = CharacterSet.alphanumerics.union(notDelimiters).inverted
 
         syntaxRules = [
             PreprocessingRule(),