diff --git a/Foundation/ISO8601DateFormatter.swift b/Foundation/ISO8601DateFormatter.swift
index 3a988e165b..d11606c504 100644
--- a/Foundation/ISO8601DateFormatter.swift
+++ b/Foundation/ISO8601DateFormatter.swift
@@ -37,6 +37,8 @@ extension ISO8601DateFormatter {
         
         public static var withColonSeparatorInTimeZone = ISO8601DateFormatter.Options(rawValue: 1 << 10)
         
+        public static var withFractionalSeconds = ISO8601DateFormatter.Options(rawValue: 1 << 11)
+        
         public static var withFullDate = ISO8601DateFormatter.Options(rawValue: withYear.rawValue + withMonth.rawValue + withDay.rawValue + withDashSeparatorInDate.rawValue)
         
         public static var withFullTime = ISO8601DateFormatter.Options(rawValue: withTime.rawValue + withTimeZone.rawValue + withColonSeparatorInTime.rawValue + withColonSeparatorInTimeZone.rawValue)
diff --git a/TestFoundation/TestISO8601DateFormatter.swift b/TestFoundation/TestISO8601DateFormatter.swift
index 3511414a46..cbf11f5713 100644
--- a/TestFoundation/TestISO8601DateFormatter.swift
+++ b/TestFoundation/TestISO8601DateFormatter.swift
@@ -20,8 +20,8 @@ class TestISO8601DateFormatter: XCTestCase {
     
     func test_stringFromDate() {
         let formatter = DateFormatter()
-        formatter.dateFormat = "yyyy/MM/dd HH:mm zzz"
-        let dateString = "2016/10/08 22:31 GMT"
+        formatter.dateFormat = "yyyy/MM/dd HH:mm:ss.SSSS zzz"
+        let dateString = "2016/10/08 22:31:00.0713 GMT"
 
         guard let someDateTime = formatter.date(from: dateString) else {
             XCTFail("DateFormatter was unable to parse '\(dateString)' using '\(formatter.dateFormat ?? "")' date format.")
@@ -44,6 +44,9 @@ class TestISO8601DateFormatter: XCTestCase {
         isoFormatter.formatOptions = .withFullTime
         XCTAssertEqual(isoFormatter.string(from: someDateTime), "22:31:00Z")
         
+        isoFormatter.formatOptions = [.withFullTime, .withFractionalSeconds]
+        XCTAssertEqual(isoFormatter.string(from: someDateTime), "22:31:00.071Z")
+        
         isoFormatter.formatOptions = .withFullDate
         XCTAssertEqual(isoFormatter.string(from: someDateTime), "2016-10-08")
         
@@ -53,9 +56,15 @@ class TestISO8601DateFormatter: XCTestCase {
         isoFormatter.formatOptions = [.withFullTime, .withFullDate, .withSpaceBetweenDateAndTime]
         XCTAssertEqual(isoFormatter.string(from: someDateTime), "2016-10-08 22:31:00Z")
         
+        isoFormatter.formatOptions = [.withFullTime, .withFullDate, .withSpaceBetweenDateAndTime, .withFractionalSeconds]
+        XCTAssertEqual(isoFormatter.string(from: someDateTime), "2016-10-08 22:31:00.071Z")
+        
         isoFormatter.formatOptions = [.withDay, .withTime]
         XCTAssertEqual(isoFormatter.string(from: someDateTime), "282T223100")
         
+        isoFormatter.formatOptions = [.withDay, .withTime, .withFractionalSeconds]
+        XCTAssertEqual(isoFormatter.string(from: someDateTime), "282T223100.071")
+        
         isoFormatter.formatOptions = [.withWeekOfYear, .withTime]
         XCTAssertEqual(isoFormatter.string(from: someDateTime), "W40T223100")
 
@@ -79,6 +88,9 @@ class TestISO8601DateFormatter: XCTestCase {
 
         isoFormatter.formatOptions = [.withWeekOfYear, .withMonth, .withTime, .withColonSeparatorInTime, .withSpaceBetweenDateAndTime, .withDashSeparatorInDate]
         XCTAssertEqual(isoFormatter.string(from: someDateTime), "10-W40 22:31:00")
+        
+        isoFormatter.formatOptions = [.withWeekOfYear, .withMonth, .withTime, .withColonSeparatorInTime, .withSpaceBetweenDateAndTime, .withDashSeparatorInDate, .withFractionalSeconds]
+        XCTAssertEqual(isoFormatter.string(from: someDateTime), "10-W40 22:31:00.071")
 
         isoFormatter.formatOptions = [.withDay, .withWeekOfYear]
         XCTAssertEqual(isoFormatter.string(from: someDateTime), "W4006")
@@ -92,6 +104,10 @@ class TestISO8601DateFormatter: XCTestCase {
         isoFormatter.formatOptions = [.withDay, .withWeekOfYear, .withMonth]
         XCTAssertEqual(isoFormatter.string(from: someDateTime), "10W4006")
 
+        // .withFractionalSeconds should be ignored if neither .withTime or .withFullTime are specified
+        isoFormatter.formatOptions = [.withDay, .withWeekOfYear, .withMonth, .withFractionalSeconds]
+        XCTAssertEqual(isoFormatter.string(from: someDateTime), "10W4006")
+        
         isoFormatter.formatOptions = [.withMonth, .withDay, .withWeekOfYear, .withDashSeparatorInDate]
         XCTAssertEqual(isoFormatter.string(from: someDateTime), "10-W40-06")