diff --git a/src/Fable.Build/Test/JavaScript.fs b/src/Fable.Build/Test/JavaScript.fs
index 27767341a..57d7a3809 100644
--- a/src/Fable.Build/Test/JavaScript.fs
+++ b/src/Fable.Build/Test/JavaScript.fs
@@ -10,10 +10,11 @@ open SimpleExec
 
 let private mainTestSourceDir = Path.Resolve("tests", "Js", "Main")
 
-let private mainTestProject =
-    Path.Resolve("tests", "Js", "Main", "Fable.Tests.fsproj")
+let private mainTestProject = Path.Resolve("tests", "Js", "Main", "Fable.Tests.fsproj")
 
-let private testReact (isWatch: bool) =
+let private mochaBin = Path.Resolve("node_modules", ".bin", "mocha")
+
+let private testReact(isWatch: bool) =
     let workingDirectory = Path.Resolve("tests", "React")
 
     Command.Run("npm", "install", workingDirectory = workingDirectory)
@@ -21,7 +22,10 @@ let private testReact (isWatch: bool) =
     if isWatch then
         Async.Parallel
             [
-                Command.WatchFableAsync(CmdLine.appendRaw "--noCache", workingDirectory = workingDirectory)
+                Command.WatchFableAsync(
+                    CmdLine.appendRaw "--noCache",
+                    workingDirectory = workingDirectory
+                )
                 |> Async.AwaitTask
 
                 Command.RunAsync("npx", "jest --watch", workingDirectory = workingDirectory)
@@ -34,7 +38,7 @@ let private testReact (isWatch: bool) =
 
         Command.Run("npx", "jest", workingDirectory = workingDirectory)
 
-let private testAdaptive (isWatch: bool) =
+let private testAdaptive(isWatch: bool) =
     let folderName = "Adaptive"
     let sourceDir = Path.Resolve("tests", "Js", folderName)
 
@@ -42,8 +46,9 @@ let private testAdaptive (isWatch: bool) =
 
     let mochaCommand =
         CmdLine.empty
-        |> CmdLine.appendRaw "npx"
-        |> CmdLine.appendRaw "mocha"
+        |> CmdLine.appendRaw "node"
+        |> CmdLine.appendRaw "--enable-experimental-regexp-engine"
+        |> CmdLine.appendRaw mochaBin
         |> CmdLine.appendRaw destinationDir
         |> CmdLine.appendPrefix "--reporter" "dot"
         |> CmdLine.appendPrefix "-t" "10000"
@@ -83,8 +88,9 @@ let private handleMainTests (isWatch: bool) (noDotnet: bool) =
 
     let mochaCommand =
         CmdLine.empty
-        |> CmdLine.appendRaw "npx"
-        |> CmdLine.appendRaw "mocha"
+        |> CmdLine.appendRaw "node"
+        |> CmdLine.appendRaw "--enable-experimental-regexp-engine"
+        |> CmdLine.appendRaw mochaBin
         |> CmdLine.appendRaw destinationDir
         |> CmdLine.appendPrefix "--reporter" "dot"
         |> CmdLine.appendPrefix "-t" "10000"
@@ -129,7 +135,11 @@ let private handleMainTests (isWatch: bool) (noDotnet: bool) =
         |> Async.RunSynchronously
         |> ignore
     else
-        Command.Run("dotnet", "run -c Release", workingDirectory = Path.Combine("tests", "Js", "Main"))
+        Command.Run(
+            "dotnet",
+            "run -c Release",
+            workingDirectory = Path.Combine("tests", "Js", "Main")
+        )
 
         // Test the Main tests against JavaScript
         Command.Fable(fableArgs, workingDirectory = destinationDir)
@@ -143,7 +153,7 @@ let private handleMainTests (isWatch: bool) (noDotnet: bool) =
 // if isCI.IsSome then
 //     Standalone.handleStandaloneFast ()
 
-let handle (args: string list) =
+let handle(args: string list) =
     let isReactOnly = args |> List.contains "--react-only"
     let isStandaloneOnly = args |> List.contains "--standalone-only"
     let isAdaptiveOnly = args |> List.contains "--adaptive-only"
@@ -155,7 +165,8 @@ let handle (args: string list) =
     | (true, true, _)
     | (true, _, true)
     | (_, true, true) ->
-        failwith "Cannot use '--react-only', '--standalone-only' and '--adaptive-only' at the same time"
+        failwith
+            "Cannot use '--react-only', '--standalone-only' and '--adaptive-only' at the same time"
 
     | _ -> ()
 
diff --git a/src/fable-library-ts/RegExp.ts b/src/fable-library-ts/RegExp.ts
index 39999d2ed..924791d0e 100644
--- a/src/fable-library-ts/RegExp.ts
+++ b/src/fable-library-ts/RegExp.ts
@@ -7,11 +7,16 @@ export function create(pattern: string, options = 0) {
   // * Compiled:    0x0008 (ignored)
   // * Singleline:  0x0010
   // * ECMAScript:  0x0100 (ignored)
-  if ((options & ~(1 ^ 2 ^ 8 ^ 16 ^ 256)) !== 0) {
-    throw new Error("RegexOptions only supports: IgnoreCase, Multiline, Compiled, Singleline and ECMAScript");
+  // * NonBacktracking:  0x0400
+  if ((options & ~(1 ^ 2 ^ 8 ^ 16 ^ 256 ^ 1024)) !== 0) {
+    throw new Error("RegexOptions only supports: IgnoreCase, Multiline, Compiled, Singleline, ECMAScript and NonBacktracking");
   }
-  // Set always global and unicode flags for compatibility with dotnet, see #2925
-  let flags = "gu";
+
+  let flags = "";
+  // Set global and unicode flags for compatibility with dotnet, see #2925
+  // for NonBacktracking, add just 'l', ('u' + 'l' is unsupported, 'g' + 'l'
+  // is supported only with '--enable-experimental-regexp-engine')
+  flags += options & 1024 ? "l" : "gu";
   flags += options & 1 ? "i" : ""; // 0x0001 RegexOptions.IgnoreCase
   flags += options & 2 ? "m" : "";
   flags += options & 16 ? "s" : "";
diff --git a/tests/Js/Main/RegexTests.fs b/tests/Js/Main/RegexTests.fs
index d30892485..2a8f12a81 100644
--- a/tests/Js/Main/RegexTests.fs
+++ b/tests/Js/Main/RegexTests.fs
@@ -37,6 +37,37 @@ let tests =
         let r = Regex("[a-z]", options)
         int r.Options |> equal 257
 
+    testCase "RegexOptions.NonBacktracking = 1024" <| fun _ ->
+        let options = RegexOptions.NonBacktracking
+        int options |> equal 1024
+
+    // these tests depend on 'node --enable-experimental-regexp-engine' or
+    // a newer version of V8 that supports 'l' flag
+    // /lu (with unicode) is not supported
+    // /lm (with multiline) is not supported
+    testCase "Nonbacktracking regex tests" <| fun _ ->
+        let none = RegexOptions.None
+        let nonb = RegexOptions.NonBacktracking
+        // let ignorecase = RegexOptions.IgnoreCase
+        // let multilineignorecase = multiline ||| ignorecase
+
+        let sameResult extraopts str pat =
+            let result1 = Regex.Match(str, pat, none ||| extraopts).Success
+            let result2 = Regex.Match(str, pat, nonb ||| extraopts).Success
+            equal result1 result2
+
+        let str = "For more information, see Chapter 3.4.5.1"
+        sameResult none str "Chapter \d+(\.\d)*"
+        sameResult none str "chapter \d+(\.\d)*"
+
+        // some combinations of settings are not allowed with linear:
+        // Invalid regular expression: /ab\ncd/ilm: Cannot be executed in linear time
+        // sameResult multilineignorecase "^ab" "ab\ncd"
+        // sameResult multilineignorecase "^cd" "ab\ncd"
+        // sameResult multilineignorecase "^AB" "ab\ncd"
+        // sameResult multilineignorecase "^bc" "ab\ncd"
+
+
     testCase "Regex.IsMatch with IgnoreCase and Multiline works" <| fun _ ->
         let str = "ab\ncd"
         let option1 = RegexOptions.IgnoreCase