diff --git a/src/java.base/share/classes/java/net/ProxySelector.java b/src/java.base/share/classes/java/net/ProxySelector.java
index f29c6738c52d4..40e11ef54e533 100644
--- a/src/java.base/share/classes/java/net/ProxySelector.java
+++ b/src/java.base/share/classes/java/net/ProxySelector.java
@@ -27,7 +27,6 @@
 
 import java.io.IOException;
 import java.util.List;
-import java.util.Locale;
 
 import sun.security.util.SecurityConstants;
 
@@ -178,7 +177,8 @@ public static void setDefault(ProxySelector ps) {
 
     /**
      * Returns a ProxySelector which uses the given proxy address for all HTTP
-     * and HTTPS requests. If proxy is {@code null} then proxying is disabled.
+     * and HTTPS requests. If {@code proxyAddress} is {@code null}
+     * then proxying is disabled.
      *
      * @param proxyAddress
      *        The address of the proxy
@@ -207,13 +207,22 @@ static class StaticProxySelector extends ProxySelector {
 
         @Override
         public void connectFailed(URI uri, SocketAddress sa, IOException e) {
+            if (uri == null || sa == null || e == null) {
+                throw new IllegalArgumentException("Arguments can't be null.");
+            }
             /* ignore */
         }
 
         @Override
-        public synchronized List<Proxy> select(URI uri) {
-            String scheme = uri.getScheme().toLowerCase(Locale.ROOT);
-            if (scheme.equals("http") || scheme.equals("https")) {
+        public List<Proxy> select(URI uri) {
+            if (uri == null) {
+                throw new IllegalArgumentException("URI can't be null");
+            }
+            String scheme = uri.getScheme();
+            if (scheme == null) {
+                throw new IllegalArgumentException("protocol can't be null");
+            }
+            if (scheme.equalsIgnoreCase("http") || scheme.equalsIgnoreCase("https")) {
                 return list;
             } else {
                 return NO_PROXY_LIST;
diff --git a/test/jdk/java/net/ProxySelector/NullArguments.java b/test/jdk/java/net/ProxySelector/NullArguments.java
index dddaa15d7e16e..6f0ce5361565a 100644
--- a/test/jdk/java/net/ProxySelector/NullArguments.java
+++ b/test/jdk/java/net/ProxySelector/NullArguments.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -22,62 +22,46 @@
  */
 
 /* @test
- * @bug 4937962
+ * @bug 4937962 8318150
  * @summary ProxySelector.connectFailed and .select never throw IllegalArgumentException
+ * @run junit NullArguments
  */
 import java.net.*;
-import java.util.List;
 import java.io.IOException;
+import java.util.stream.Stream;
+
+import org.junit.jupiter.api.Assumptions;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import static org.junit.jupiter.api.Assertions.*;
 
 public class NullArguments {
-    public static void main(String[] args) {
-        ProxySelector ps = ProxySelector.getDefault();
-        List p = null;
-        boolean ok = false;
-        if (ps != null) {
-            try {
-                p = ps.select(null);
-            } catch (IllegalArgumentException iae) {
-                System.out.println("OK");
-                ok = true;
-            }
-            if (!ok)
-                throw new RuntimeException("Expected IllegalArgumentException!");
-            URI uri = null;
-            try {
-                uri = new URI("http://java.sun.com");
-            } catch (java.net.URISyntaxException use) {
-                // can't happen
-            }
-            SocketAddress sa = new InetSocketAddress("localhost", 80);
-            IOException ioe = new IOException("dummy IOE");
-            ok = false;
-            try {
-                ps.connectFailed(uri, sa, null);
-            } catch (IllegalArgumentException iae) {
-                System.out.println("OK");
-                ok = true;
-            }
-            if (!ok)
-                throw new RuntimeException("Expected IllegalArgumentException!");
-            ok = false;
-            try {
-                ps.connectFailed(uri, null, ioe);
-            } catch (IllegalArgumentException iae) {
-                System.out.println("OK");
-                ok = true;
-            }
-            if (!ok)
-                throw new RuntimeException("Expected IllegalArgumentException!");
-            ok = false;
-            try {
-                ps.connectFailed(null, sa, ioe);
-            } catch (IllegalArgumentException iae) {
-                System.out.println("OK");
-                ok = true;
-            }
-            if (!ok)
-                throw new RuntimeException("Expected IllegalArgumentException!");
-        }
+
+    public static Stream<ProxySelector> testProxies() {
+        return Stream.of(
+                ProxySelector.getDefault(),
+                ProxySelector.of(new InetSocketAddress(1234)));
+    }
+
+    @ParameterizedTest
+    @MethodSource("testProxies")
+    void testNullArguments(ProxySelector ps) throws URISyntaxException {
+        Assumptions.assumeTrue(ps != null, "Skipping null selector");
+        assertThrows(IllegalArgumentException.class,
+                () -> ps.select(null),
+                "Expected IllegalArgumentException!");
+        URI uri = new URI("http://java.sun.com");
+        SocketAddress sa = new InetSocketAddress("localhost", 80);
+        IOException ioe = new IOException("dummy IOE");
+        assertThrows(IllegalArgumentException.class,
+                () -> ps.connectFailed(uri, sa, null),
+                "Expected IllegalArgumentException!");
+        assertThrows(IllegalArgumentException.class,
+                () -> ps.connectFailed(uri, null, ioe),
+                "Expected IllegalArgumentException!");
+        assertThrows(IllegalArgumentException.class,
+                () -> ps.connectFailed(null, sa, ioe),
+                "Expected IllegalArgumentException!");
     }
 }