diff --git a/Sources/_RegexParser/Regex/Parse/LexicalAnalysis.swift b/Sources/_RegexParser/Regex/Parse/LexicalAnalysis.swift
index b38a07e1..b9693d97 100644
--- a/Sources/_RegexParser/Regex/Parse/LexicalAnalysis.swift
+++ b/Sources/_RegexParser/Regex/Parse/LexicalAnalysis.swift
@@ -331,7 +331,9 @@ extension Parser {
   ///
   /// Diagnoses on overflow
   ///
-  mutating func lexNumber(_ kind: RadixKind = .decimal) -> AST.Atom.Number? {
+  mutating func lexNumber(
+    _ kind: RadixKind = .decimal
+  ) -> AST.Atom.Number? {
     guard let str = tryEatPrefix(kind.characterFilter) else {
       return nil
     }
@@ -342,6 +344,26 @@ extension Parser {
     return .init(i, at: str.location)
   }
 
+  /// Try to eat a quantification bound, such as appears in `/x{3,12}`
+  ///
+  /// Returns: `nil` if there's no number, otherwise the number
+  ///
+  /// Diagnoses on overflow. Currently, we will diagnose for any values over `UInt16.max`
+  ///
+  mutating func lexQuantBound() -> AST.Atom.Number? {
+    let kind = RadixKind.decimal
+    guard let str = tryEatPrefix(kind.characterFilter) else {
+      return nil
+    }
+    guard let i = UInt16(str.value, radix: kind.radix) else {
+      error(.numberOverflow(str.value), at: str.location)
+      return .init(nil, at: str.location)
+    }
+
+    return .init(Int(i), at: str.location)
+  }
+
+
   /// Expect a number of a given `kind`, diagnosing if a number cannot be
   /// parsed.
   mutating func expectNumber(_ kind: RadixKind = .decimal) -> AST.Atom.Number {
@@ -492,7 +514,7 @@ extension Parser {
 
         return p.tryEating { p in
           guard p.tryEat("{"),
-                let range = p.lexRange(trivia: &trivia),
+                let range = p.lexQuantRange(trivia: &trivia),
                 p.tryEat("}")
           else { return nil }
           return range.value
@@ -519,12 +541,14 @@ extension Parser {
   ///                  | ExpRange
   ///     ExpRange    -> '..<' <Int> | '...' <Int>
   ///                  | <Int> '..<' <Int> | <Int> '...' <Int>?
-  mutating func lexRange(trivia: inout [AST.Trivia]) -> Located<Quant.Amount>? {
+  mutating func lexQuantRange(
+    trivia: inout [AST.Trivia]
+  ) -> Located<Quant.Amount>? {
     recordLoc { p in
       p.tryEating { p in
         if let t = p.lexWhitespace() { trivia.append(t) }
 
-        let lowerOpt = p.lexNumber()
+        let lowerOpt = p.lexQuantBound()
 
         if let t = p.lexWhitespace() { trivia.append(t) }
 
@@ -546,7 +570,7 @@ extension Parser {
 
         if let t = p.lexWhitespace() { trivia.append(t) }
 
-        var upperOpt = p.lexNumber()
+        var upperOpt = p.lexQuantBound()
         if closedRange == false {
           // If we have an open range, the upper bound should be adjusted down.
           upperOpt?.value? -= 1
diff --git a/Tests/RegexTests/LexTests.swift b/Tests/RegexTests/LexTests.swift
index 53775e66..ccfd18eb 100644
--- a/Tests/RegexTests/LexTests.swift
+++ b/Tests/RegexTests/LexTests.swift
@@ -63,6 +63,25 @@ extension RegexTests {
       _ = p.lexNumber()
     }
 
+    let invalidQuantBounds: Array<String> = [
+      "65536",                       // UInt16.max + 1
+      "2147483646",                  // Int32.max  - 1
+      "9223372036854775806",         // Int64.max  - 1
+    ]
+
+    for invalidNum in invalidQuantBounds {
+      let regexes: Array<String> = [
+        "x{\(invalidNum)}",
+        "x{1,\(invalidNum)}",
+        "x{\(invalidNum),1}",
+      ]
+      for regex in regexes {
+        diagnose(regex, expecting: .numberOverflow(invalidNum)) { p in
+          _ = p.parse()
+        }
+      }
+    }
+
     // TODO: want to dummy print out source ranges, etc, test that.
   }
 
diff --git a/Tests/RegexTests/MatchTests.swift b/Tests/RegexTests/MatchTests.swift
index c52560d6..017005e5 100644
--- a/Tests/RegexTests/MatchTests.swift
+++ b/Tests/RegexTests/MatchTests.swift
@@ -751,6 +751,12 @@ extension RegexTests {
     firstMatchTest("(?U)a??", input: "a", match: "a")
     firstMatchTest("(?U)a??a", input: "aaa", match: "aa")
 
+    // Quantification syntax is somewhat dependent on the contents.
+    // In JS, PCRE2, Python, and some others, /x{-1}/ will be literally "x{-1}"
+    // Note that Java8 and Rust throw an (unhelpful) error
+    firstMatchTest("x{-1}", input: "x{-1}", match: "x{-1}")
+    firstMatchTest("x{-1}", input: "xax{-2}bx{-1}c", match: "x{-1}")
+
     // TODO: After captures, easier to test these
   }