diff --git a/CHANGELOG.md b/CHANGELOG.md
index ea122f9ff..095f88bef 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,9 @@ The release run heads these entries with the version and opens a fresh
 
 ## Unreleased
 
+- Apple CSV decoding rejects multi-character and multibyte delimiters.
+  Roots without a text-root interface are exposed as `Element`, not `TextRoot`.
+
 - Apple `Measure(string:)` is now failable. An invalid length returns `nil`
   instead of letting a C++ exception escape into Swift.
 
diff --git a/apple/include/OdrCoreObjC/ODRFile.h b/apple/include/OdrCoreObjC/ODRFile.h
index fbfb6481d..307872c06 100644
--- a/apple/include/OdrCoreObjC/ODRFile.h
+++ b/apple/include/OdrCoreObjC/ODRFile.h
@@ -228,9 +228,9 @@ NS_SWIFT_NAME(CsvOptions)
 @interface ODRCsvOptions : NSObject
 /// `nil` to detect.
 @property(nonatomic, strong, nullable) NSNumber *encoding;
-/// A one-character string, `nil` to detect.
+/// One ASCII character, `nil` or empty to detect. Other strings fail decoding.
 @property(nonatomic, copy, nullable) NSString *separator;
-/// A one-character string, `nil` to detect.
+/// One ASCII character, `nil` or empty to detect. Other strings fail decoding.
 @property(nonatomic, copy, nullable) NSString *quote;
 @end
 
diff --git a/apple/src/ODRDocumentElement.mm b/apple/src/ODRDocumentElement.mm
index 97363e3ed..278770352 100644
--- a/apple/src/ODRDocumentElement.mm
+++ b/apple/src/ODRDocumentElement.mm
@@ -102,7 +102,9 @@ + (nullable ODRElement *)elementWithHandle:(odr::Element)handle
   Class klass = [ODRElement class];
   switch (handle.type()) {
   case odr::ElementType::root:
-    klass = [ODRTextRoot class];
+    if (handle.as_text_root()) {
+      klass = [ODRTextRoot class];
+    }
     break;
   case odr::ElementType::slide:
     klass = [ODRSlide class];
diff --git a/apple/src/ODRFile.mm b/apple/src/ODRFile.mm
index 507adafcc..a68434f3b 100644
--- a/apple/src/ODRFile.mm
+++ b/apple/src/ODRFile.mm
@@ -8,6 +8,7 @@
 
 #include <optional>
 #include <sstream>
+#include <stdexcept>
 #include <vector>
 
 using odr::apple::guarded;
@@ -143,6 +144,18 @@
   return result;
 }
 
+std::optional<char> csv_delimiter(NSString *const value) {
+  // an empty string means unset rather than a NUL
+  if (value.length == 0) {
+    return std::nullopt;
+  }
+  const std::string bytes = to_string(value);
+  if (bytes.size() != 1) {
+    throw std::invalid_argument("CSV delimiter must be one UTF-8 byte");
+  }
+  return bytes.front();
+}
+
 /// `nil` for an unset `std::optional`, the way a Java binding would use -1.
 NSString *_Nullable to_nsstring(const std::optional<std::string> &value) {
   return value.has_value() ? to_nsstring(*value) : nil;
@@ -370,13 +383,8 @@ + (nullable instancetype)decodePath:(NSString *)path
       native.csv.encoding =
           static_cast<odr::TextEncoding>(options.csv.encoding.integerValue);
     }
-    // one character, and an empty string means unset rather than a NUL
-    if (options.csv.separator.length > 0) {
-      native.csv.separator = [options.csv.separator characterAtIndex:0];
-    }
-    if (options.csv.quote.length > 0) {
-      native.csv.quote = [options.csv.quote characterAtIndex:0];
-    }
+    native.csv.separator = csv_delimiter(options.csv.separator);
+    native.csv.quote = csv_delimiter(options.csv.quote);
     return [ODRDecodedFile
         decodedFileWithHandle:odr::open(to_string(path), native)];
   });
diff --git a/apple/tests/OdrCoreTests.swift b/apple/tests/OdrCoreTests.swift
index b844f78ac..06c2710de 100644
--- a/apple/tests/OdrCoreTests.swift
+++ b/apple/tests/OdrCoreTests.swift
@@ -118,7 +118,29 @@ final class DecodeTests: XCTestCase {
 
     let csv = try decoded.asCsvFile()
     XCTAssertEqual(try csv.textFile().text(), "a,b\n1,2\n")
-    XCTAssertNotNil(try csv.document().rootElement())
+    let root = try XCTUnwrap(try csv.document().rootElement())
+    XCTAssertFalse(root is TextRoot)
+    XCTAssertNotNil(root.firstDescendant(ofType: Sheet.self))
+  }
+
+  func testCsvDelimitersMustBeSingleBytes() throws {
+    let path = try write("a;b\nc;d\n", as: "table.csv")
+    let options = DecodeOptions()
+    options.csv.separator = ";"
+    let csv = try DecodedFile.decode(path: path, options: options).asCsvFile()
+    let root = try XCTUnwrap(try csv.document().rootElement())
+    let sheet = try XCTUnwrap(root.firstDescendant(ofType: Sheet.self))
+    XCTAssertEqual(sheet.dimensions.columns, 2)
+    options.csv.quote = ""
+    XCTAssertNoThrow(try DecodedFile.decode(path: path, options: options))
+    for invalid in [";,", "é", "😀"] {
+      options.csv.separator = invalid
+      XCTAssertThrowsError(try DecodedFile.decode(path: path, options: options), invalid)
+      options.csv.separator = ";"
+      options.csv.quote = invalid
+      XCTAssertThrowsError(try DecodedFile.decode(path: path, options: options), invalid)
+      options.csv.quote = nil
+    }
   }
 
   /// `odr::Filesystem::exists("")` throws `std::invalid_argument`. Unguarded,