diff --git a/src/core/IronPython.Modules/nt.cs b/src/core/IronPython.Modules/nt.cs
index dbc80ff0d..239d0c313 100644
--- a/src/core/IronPython.Modules/nt.cs
+++ b/src/core/IronPython.Modules/nt.cs
@@ -1144,7 +1144,7 @@ private static Process MakeProcess() {
 
         private static object SpawnProcessImpl(CodeContext/*!*/ context, Process process, int mode, string path, object? args, [CallerMemberName] string? methodname = null) {
             try {
-                process.StartInfo.Arguments = ArgumentsToString(context, args, methodname);
+                SetArguments(process.StartInfo, ArgumentsToList(context, args, methodname));
                 process.StartInfo.FileName = path;
                 process.StartInfo.UseShellExecute = false;
             } catch (Exception e) {
@@ -1179,6 +1179,48 @@ private static object SpawnProcessImpl(CodeContext/*!*/ context, Process process
                 _processToIdMapping[id] = process;
                 return ScriptingRuntimeHelpers.Int32ToObject(id);
             }
+
+            // Set the process arguments from the list of args
+            static void SetArguments(ProcessStartInfo startInfo, List<string> args) {
+                if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) {
+                    startInfo.Arguments = string.Join(" ", args);
+                    return;
+                }
+
+#if NET
+                foreach (var arg in args) {
+                    startInfo.ArgumentList.Add(arg);
+                }
+#else
+                startInfo.Arguments = string.Join(" ", args.Select(QuoteIfNeeded));
+
+                static string QuoteIfNeeded(string str) {
+                    if (str.Contains(' ')) {
+                        return "\"" + str.Replace("\"", "\"\"") + "\"";
+                    }
+                    return str;
+                }
+#endif
+            }
+
+            static List<string> ArgumentsToList(CodeContext/*!*/ context, object? args, string? methodname) {
+                IEnumerator? argsEnumerator;
+                if (!PythonOps.TryGetEnumerator(context, args, out argsEnumerator)) {
+                    throw PythonOps.TypeErrorForBadInstance("args parameter must be sequence, not {0}", args);
+                }
+
+                var list = new List<string>();
+                try {
+                    // skip the first element, which is the name of the command being run
+                    argsEnumerator.MoveNext();
+                    while (argsEnumerator.MoveNext()) {
+                        list.Add(ConvertToFsString(context, argsEnumerator.Current, "elements of 'args'", methodname));
+                    }
+                } finally {
+                    (argsEnumerator as IDisposable)?.Dispose();
+                }
+                return list;
+            }
         }
 
         /// <summary>
@@ -1201,45 +1243,6 @@ private static void SetEnvironment(CodeContext context, System.Collections.Speci
         }
 #endif
 
-        /// <summary>
-        /// Convert a sequence of args to a string suitable for using to spawn a process.
-        /// </summary>
-        private static string ArgumentsToString(CodeContext/*!*/ context, object? args, string? methodname) {
-            IEnumerator? argsEnumerator;
-            StringBuilder? sb = null;
-            if (!PythonOps.TryGetEnumerator(context, args, out argsEnumerator)) {
-                throw PythonOps.TypeErrorForBadInstance("args parameter must be sequence, not {0}", args);
-            }
-
-            bool space = false;
-            try {
-                // skip the first element, which is the name of the command being run
-                argsEnumerator.MoveNext();
-                while (argsEnumerator.MoveNext()) {
-                    if (sb == null) sb = new StringBuilder(); // lazy creation
-                    string strarg = ConvertToFsString(context, argsEnumerator.Current, "elements of 'args'", methodname);
-                    if (space) {
-                        sb.Append(' ');
-                    }
-                    if (strarg.Contains(' ')) {
-                        sb.Append('"');
-                        // double quote any existing quotes
-                        sb.Append(strarg.Replace("\"", "\"\""));
-                        sb.Append('"');
-                    } else {
-                        sb.Append(strarg);
-                    }
-                    space = true;
-                }
-            } finally {
-                IDisposable? disposable = argsEnumerator as IDisposable;
-                if (disposable != null) disposable.Dispose();
-            }
-
-            if (sb == null) return "";
-            return sb.ToString();
-        }
-
 #if FEATURE_PROCESS
         [SupportedOSPlatform("windows"), PythonHidden(PlatformsAttribute.PlatformFamily.Unix)]
         public static void startfile([NotNone] string filepath, string operation = "open") {
diff --git a/tests/suite/modules/system_related/test_nt.py b/tests/suite/modules/system_related/test_nt.py
index 95d02e284..bed9137c2 100644
--- a/tests/suite/modules/system_related/test_nt.py
+++ b/tests/suite/modules/system_related/test_nt.py
@@ -902,7 +902,6 @@ def test__getfullpathname_neg(self):
         for bad in [None, 0, 34, -big(12345), 3.14, object, self.test__getfullpathname]:
             self.assertRaises(TypeError, nt._getfullpathname, bad)
 
-    @unittest.skipIf(is_netcoreapp, 'TODO: figure out')
     @unittest.skipUnless(sys.platform == "win32", 'windir is Windows specific')
     def test_cp15514(self):
         cmd_variation_list = ['%s -c "print(__name__)"' % sys.executable,
diff --git a/tests/suite/test_stdconsole.py b/tests/suite/test_stdconsole.py
index a40e9c6be..51205e701 100644
--- a/tests/suite/test_stdconsole.py
+++ b/tests/suite/test_stdconsole.py
@@ -68,8 +68,8 @@ def setUp(self):
     #       "lastline"  : valuestring is compared against the last line of the output
     #       "regexp"    : valuestring is a regular expression compared against the entire output
     def TestCommandLine(self, args, expected_output, expected_exitcode = 0):
-        if not is_cli:
-            # https://github.com/IronLanguages/ironpython3/issues/648
+        if os.name == 'nt':
+            # must self-quote arguments with spawnv on Windows
             try:
                 idx = args.index("-c")
                 if idx + 1 < len(args):