diff --git a/Sources/_MatchingEngine/Regex/AST/ASTProtocols.swift b/Sources/_MatchingEngine/Regex/AST/ASTProtocols.swift
index 6db35dc8c..b6c17f399 100644
--- a/Sources/_MatchingEngine/Regex/AST/ASTProtocols.swift
+++ b/Sources/_MatchingEngine/Regex/AST/ASTProtocols.swift
@@ -51,7 +51,13 @@ extension _ASTPrintable {
   public var debugDescription: String { _dump() }
 
   var _children: [AST]? {
-    (self as? _ASTParent)?.children
+    if let children = (self as? _ASTParent)?.children {
+      return children
+    }
+    if let children = (self as? AST)?.children {
+      return children
+    }
+    return nil
   }
 
   func _print() -> String {
@@ -62,8 +68,13 @@ extension _ASTPrintable {
     guard let children = _children else {
       return _dumpBase
     }
-    let sub = children.lazy.map {
-      $0._dump()
+    let sub = children.lazy.compactMap {
+      // Exclude trivia for now, as we don't want it to appear when performing
+      // comparisons of dumped output in tests.
+      // TODO: We should eventually have some way of filtering out trivia for
+      // tests, so that it can appear in regular dumps.
+      if $0.isTrivia { return nil }
+      return $0._dump()
     }.joined(separator: ",")
     return "\(_dumpBase)(\(sub))"
   }
diff --git a/Sources/_MatchingEngine/Regex/AST/CustomCharClass.swift b/Sources/_MatchingEngine/Regex/AST/CustomCharClass.swift
index b935d0a31..8c8b356f0 100644
--- a/Sources/_MatchingEngine/Regex/AST/CustomCharClass.swift
+++ b/Sources/_MatchingEngine/Regex/AST/CustomCharClass.swift
@@ -53,8 +53,19 @@ extension CustomCC {
 
 extension CustomCC: _ASTNode {
   public var _dumpBase: String {
-    // FIXME: print out members...
-    "customCharacterClass"
+    "customCharacterClass(\(members))"
   }
 }
 
+extension CustomCC.Member: _ASTPrintable {
+  public var _dumpBase: String {
+    switch self {
+    case .custom(let cc): return "\(cc)"
+    case .atom(let a): return "\(a)"
+    case .range(let lhs, let rhs):
+      return "range \(lhs) to \(rhs)"
+    case .setOperation(let lhs, let op, let rhs):
+      return "op \(lhs) \(op.value) \(rhs)"
+    }
+  }
+}
diff --git a/Sources/_MatchingEngine/Regex/AST/Group.swift b/Sources/_MatchingEngine/Regex/AST/Group.swift
index bb0aa8194..c8713ca49 100644
--- a/Sources/_MatchingEngine/Regex/AST/Group.swift
+++ b/Sources/_MatchingEngine/Regex/AST/Group.swift
@@ -71,7 +71,7 @@ extension AST.Group.Kind: _ASTPrintable {
   public var _dumpBase: String {
     switch self {
     case .capture:             return "capture"
-    case .namedCapture(let s): return "capture<\(s)>"
+    case .namedCapture(let s): return "capture<\(s.value)>"
     case .nonCapture:          return "nonCapture"
     case .nonCaptureReset:     return "nonCaptureReset"
     case .atomicNonCapturing:  return "atomicNonCapturing"
diff --git a/Tests/RegexTests/ParseTests.swift b/Tests/RegexTests/ParseTests.swift
index c44225249..e918c5aec 100644
--- a/Tests/RegexTests/ParseTests.swift
+++ b/Tests/RegexTests/ParseTests.swift
@@ -57,6 +57,19 @@ func parseWithDelimitersTest(_ input: String, _ expecting: AST) {
   }
 }
 
+/// Make sure the AST for two regex strings get compared differently.
+func parseNotEqualTest(_ lhs: String, _ rhs: String,
+                       syntax: SyntaxOptions = .traditional) {
+  let lhsAST = try! parse(lhs, syntax)
+  let rhsAST = try! parse(rhs, syntax)
+  if lhsAST == rhsAST || lhsAST._dump() == rhsAST._dump() {
+    XCTFail("""
+              AST: \(lhsAST._dump())
+              Should not be equal to: \(rhsAST._dump())
+              """)
+  }
+}
+
 extension RegexTests {
   func testParse() {
     parseTest(
@@ -194,6 +207,16 @@ extension RegexTests {
     parseTest("[[:word:]]", charClass(posixProp_m(.posix(.word))))
     parseTest("[[:xdigit:]]", charClass(posixProp_m(.posix(.xdigit))))
 
+    parseTest("[[:ascii:]]", charClass(posixProp_m(.ascii)))
+    parseTest("[[:cntrl:]]", charClass(posixProp_m(.generalCategory(.control))))
+    parseTest("[[:digit:]]", charClass(posixProp_m(.generalCategory(.decimalNumber))))
+    parseTest("[[:lower:]]", charClass(posixProp_m(.binary(.lowercase))))
+    parseTest("[[:punct:]]", charClass(posixProp_m(.generalCategory(.punctuation))))
+    parseTest("[[:space:]]", charClass(posixProp_m(.binary(.whitespace))))
+    parseTest("[[:upper:]]", charClass(posixProp_m(.binary(.uppercase))))
+
+    parseTest("[[:UPPER:]]", charClass(posixProp_m(.binary(.uppercase))))
+
     parseTest("[[:isALNUM:]]", charClass(posixProp_m(.posix(.alnum))))
     parseTest("[[:AL_NUM:]]", charClass(posixProp_m(.posix(.alnum))))
     parseTest("[[:script=Greek:]]", charClass(posixProp_m(.script(.greek))))
@@ -436,6 +459,24 @@ extension RegexTests {
     parseWithDelimitersTest("'/a b/'", concat("a", " ", "b"))
     parseWithDelimitersTest("'|a b|'", concat("a", "b"))
 
+    // Make sure dumping output correctly reflects differences in AST.
+    parseNotEqualTest(#"abc"#, #"abd"#)
+
+    parseNotEqualTest(#"[abc[:space:]\d]+"#,
+                      #"[abc[:upper:]\d]+"#)
+
+    parseNotEqualTest(#"[abc[:space:]\d]+"#,
+                      #"[ac[:space:]\d]+"#)
+
+    parseNotEqualTest(#"[abc[:space:]\d]+"#,
+                      #"[acc[:space:]\s]+"#)
+
+    parseNotEqualTest(#"[abc[:space:]\d]+"#,
+                      #"[acc[:space:]\d]*"#)
+
+    parseNotEqualTest(#"([a-c&&e]*)+"#,
+                      #"([a-d&&e]*)+"#)
+
     // TODO: failure tests
   }
 
diff --git a/Tests/RegexTests/SyntaxOptionsTests.swift b/Tests/RegexTests/SyntaxOptionsTests.swift
index f771e84e6..34c8c240a 100644
--- a/Tests/RegexTests/SyntaxOptionsTests.swift
+++ b/Tests/RegexTests/SyntaxOptionsTests.swift
@@ -7,6 +7,8 @@ private let dplus = oneOrMore(
   .greedy, atom(.escaped(.decimalDigit)))
 private let dotAST = concat(
   dplus, ".", dplus, ".", dplus, ".", dplus)
+private let dotASTQuoted = concat(
+  dplus, quote("."), dplus, quote("."), dplus, quote("."), dplus)
 
 extension RegexTests {
 
@@ -42,7 +44,7 @@ extension RegexTests {
       dotAST, syntax: .modern)
     parseTest(
       #" \d+ "." \d+ "." \d+ "." \d+ "#,
-      dotAST, syntax: .modern)
+      dotASTQuoted, syntax: .modern)
   }
 
   func testModernRanges() {