diff --git a/src/libraries/System.Private.Runtime.InteropServices.JavaScript/tests/System/Runtime/InteropServices/JavaScript/JavaScriptTests.cs b/src/libraries/System.Private.Runtime.InteropServices.JavaScript/tests/System/Runtime/InteropServices/JavaScript/JavaScriptTests.cs
index 005e54ac03f0d5..16e4ffd7cedc55 100644
--- a/src/libraries/System.Private.Runtime.InteropServices.JavaScript/tests/System/Runtime/InteropServices/JavaScript/JavaScriptTests.cs
+++ b/src/libraries/System.Private.Runtime.InteropServices.JavaScript/tests/System/Runtime/InteropServices/JavaScript/JavaScriptTests.cs
@@ -95,10 +95,10 @@ public static void FunctionSum()
         public static void FunctionMath()
         {
             JSObject math = (JSObject)Runtime.GetGlobalObject("Math");
-            Assert.NotNull(math);
+            Assert.True(math != null, "math != null");
 
             Function mathMax = (Function)math.GetObjectProperty("max");
-            Assert.NotNull(mathMax);
+            Assert.True(mathMax != null, "mathMax != null");
 
             var maxValue = (int)mathMax.Apply(null, new object[] { 5, 6, 2, 3, 7 });
             Assert.Equal(7, maxValue);
@@ -107,7 +107,7 @@ public static void FunctionMath()
             Assert.Equal(7, maxValue);
 
             Function mathMin = (Function)((JSObject)Runtime.GetGlobalObject("Math")).GetObjectProperty("min");
-            Assert.NotNull(mathMin);
+            Assert.True(mathMin != null, "mathMin != null");
 
             var minValue = (int)mathMin.Apply(null, new object[] { 5, 6, 2, 3, 7 });
             Assert.Equal(2, minValue);
@@ -115,5 +115,39 @@ public static void FunctionMath()
             minValue = (int)mathMin.Call(null, 5, 6, 2, 3, 7);
             Assert.Equal(2, minValue);
         }
+
+        private static string GetBigTestString() {
+            var expectedSb = new System.Text.StringBuilder();
+            expectedSb.Append("start<<<");
+            for (int i = 0; i < 4096000; i++)
+                expectedSb.Append(i % 10);
+            expectedSb.Append(">>>end");
+            return expectedSb.ToString();
+        }
+
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/42693")]
+        [Fact]
+        public static void InvokeJSMarshalsStrings() {
+            var invokeResult = Runtime.InvokeJS("\"a\0bc\"");
+            Assert.Equal("a\0bc", invokeResult);
+
+            var expected = GetBigTestString();
+            invokeResult = Runtime.InvokeJS("\"" + expected + "\"");
+            Assert.Equal(expected, invokeResult);
+        }
+
+        [Fact]
+        public static void MarshalStringParametersFromJS() {
+            HelperMarshal._stringResource = null;
+            Runtime.InvokeJS("App.call_test_method(\"InvokeString\", [\"a\0bc\"])");
+            Assert.Equal("a\0bc", HelperMarshal._stringResource);
+
+            var expected = GetBigTestString();
+            for (var i = 0; i < 10; i++) {
+                HelperMarshal._stringResource = null;
+                Runtime.InvokeJS("App.call_test_method(\"InvokeString\", [\"" + expected + "\"])");
+                Assert.Equal(expected, HelperMarshal._stringResource);
+            }
+        }
     }
 }
diff --git a/src/mono/wasm/runtime/binding_support.js b/src/mono/wasm/runtime/binding_support.js
index 5131c7f678dcc3..59b229678d857d 100644
--- a/src/mono/wasm/runtime/binding_support.js
+++ b/src/mono/wasm/runtime/binding_support.js
@@ -52,7 +52,7 @@ var BindingSupportLib = {
 			this.find_method = Module.cwrap ('mono_wasm_assembly_find_method', 'number', ['number', 'string', 'number']);
 			this.invoke_method = Module.cwrap ('mono_wasm_invoke_method', 'number', ['number', 'number', 'number', 'number']);
 			this.mono_string_get_utf8 = Module.cwrap ('mono_wasm_string_get_utf8', 'number', ['number']);
-			this.js_string_to_mono_string = Module.cwrap ('mono_wasm_string_from_js', 'number', ['string']);
+			this.mono_wasm_string_from_utf16 = Module.cwrap ('mono_wasm_string_from_utf16', 'number', ['number', 'number']);
 			this.mono_get_obj_type = Module.cwrap ('mono_wasm_get_obj_type', 'number', ['number']);
 			this.mono_unbox_int = Module.cwrap ('mono_unbox_int', 'number', ['number']);
 			this.mono_unbox_float = Module.cwrap ('mono_wasm_unbox_float', 'number', ['number']);
@@ -140,6 +140,23 @@ var BindingSupportLib = {
 			return this.call_method (this.is_simple_array, null, "mi", [ ele ]);
 		},
 
+		js_string_to_mono_string: function (string) {
+			if (string === null || typeof string === "undefined")
+				return 0;
+
+			var buffer = Module._malloc (string.length * 2);
+			if (!buffer)
+				throw new Error ("out of memory");
+
+			var buffer16 = (buffer / 2) | 0;
+			for (var i = 0; i < string.length; i++)
+				Module.HEAP16[buffer16 + i] = string.charCodeAt (i);
+			
+			var result = this.mono_wasm_string_from_utf16 (buffer, string.length);
+			Module._free (buffer);
+			return result;
+		},
+		
 		mono_array_to_js_array: function (mono_array) {
 			if (mono_array == 0)
 				return null;
diff --git a/src/mono/wasm/runtime/driver.c b/src/mono/wasm/runtime/driver.c
index 250f20fe8a712e..90fbc5453aa3a1 100644
--- a/src/mono/wasm/runtime/driver.c
+++ b/src/mono/wasm/runtime/driver.c
@@ -604,6 +604,17 @@ mono_wasm_string_from_js (const char *str)
 		return NULL;
 }
 
+EMSCRIPTEN_KEEPALIVE MonoString *
+mono_wasm_string_from_utf16 (const mono_unichar2 * chars, int length)
+{
+	assert (length >= 0);
+
+	if (chars)
+		return mono_string_new_utf16 (root_domain, chars, length);
+	else
+		return NULL;
+}
+
 static int
 class_is_task (MonoClass *klass)
 {