diff --git a/java/libphonenumber/src/com/google/i18n/phonenumbers/PhoneNumberUtil.java b/java/libphonenumber/src/com/google/i18n/phonenumbers/PhoneNumberUtil.java
index a1d83b3070..30dfd9c74a 100644
--- a/java/libphonenumber/src/com/google/i18n/phonenumbers/PhoneNumberUtil.java
+++ b/java/libphonenumber/src/com/google/i18n/phonenumbers/PhoneNumberUtil.java
@@ -328,9 +328,9 @@ public class PhoneNumberUtil {
   // defined in RFC3966.
   private static final String ALPHANUM = VALID_ALPHA + DIGITS;
   private static final String RFC3966_DOMAINLABEL =
-      "[" + ALPHANUM + "]+((\\-)*[" + ALPHANUM + "])*";
+      "[" + ALPHANUM + "]+(\\-+[" + ALPHANUM + "]+)*";
   private static final String RFC3966_TOPLABEL =
-      "[" + VALID_ALPHA + "]+((\\-)*[" + ALPHANUM + "])*";
+      "[" + VALID_ALPHA + "]+(\\-+[" + ALPHANUM + "]+)*";
   private static final String RFC3966_DOMAINNAME =
       "^(" + RFC3966_DOMAINLABEL + "\\.)*" + RFC3966_TOPLABEL + "\\.?$";
   static final Pattern RFC3966_DOMAINNAME_PATTERN = Pattern.compile(RFC3966_DOMAINNAME);
diff --git a/java/libphonenumber/test/com/google/i18n/phonenumbers/PhoneNumberUtilTest.java b/java/libphonenumber/test/com/google/i18n/phonenumbers/PhoneNumberUtilTest.java
index 4da210ec1d..7b0f672add 100644
--- a/java/libphonenumber/test/com/google/i18n/phonenumbers/PhoneNumberUtilTest.java
+++ b/java/libphonenumber/test/com/google/i18n/phonenumbers/PhoneNumberUtilTest.java
@@ -31,6 +31,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
+import java.util.regex.Pattern;
 import org.junit.Assert;
 import org.junit.function.ThrowingRunnable;
 import org.mockito.Mockito;
@@ -2221,6 +2222,41 @@ public void testParseMaliciousInput() throws Exception {
     }
   }
 
+  public void testParseRFC3966PhoneContextDomainname() throws Exception {
+    // Domain phone-contexts keep parsing, including labels with single or repeated hyphens.
+    assertEquals(US_LOCAL_NUMBER,
+        phoneUtil.parse("tel:253-0000;phone-context=www.google.com", RegionCode.US));
+    assertEquals(US_LOCAL_NUMBER,
+        phoneUtil.parse("tel:253-0000;phone-context=ex--ample.domain.com", RegionCode.US));
+
+    // A long ambiguous domain is rejected. The old label pattern ([alnum]+((\-)*[alnum])*) made
+    // backtracking engines in the JS and Python ports of this pattern spend minutes on this
+    // input; Java's own matcher prunes it, this pins the rejection and the accepted language.
+    StringBuilder evilContext = new StringBuilder(100);
+    for (int i = 0; i < 25; i++) {
+      evilContext.append("aa.");
+    }
+    evilContext.append("aa!");
+    try {
+      phoneUtil.parse("tel:253-0000;phone-context=" + evilContext, RegionCode.US);
+      fail("This should not parse without throwing an exception.");
+    } catch (NumberParseException e) {
+      // Expected this exception.
+    }
+
+    // The rewritten label matches alnum runs separated by one or more hyphens, but not labels
+    // with leading/trailing hyphens or empty labels.
+    Pattern domainname = PhoneNumberUtil.RFC3966_DOMAINNAME_PATTERN;
+    assertTrue(domainname.matcher("a.b.c").matches());
+    assertTrue(domainname.matcher("ab-cd.ef").matches());
+    assertTrue(domainname.matcher("a--b.c").matches());
+    assertTrue(domainname.matcher("example.com.").matches());
+    assertFalse(domainname.matcher("aa.bb-").matches());
+    assertFalse(domainname.matcher("aa..bb").matches());
+    assertFalse(domainname.matcher("-aa.bb").matches());
+    assertFalse(domainname.matcher("a-.b").matches());
+  }
+
   public void testParseWithInternationalPrefixes() throws Exception {
     assertEquals(US_NUMBER, phoneUtil.parse("+1 (650) 253-0000", RegionCode.NZ));
     assertEquals(INTERNATIONAL_TOLL_FREE, phoneUtil.parse("011 800 1234 5678", RegionCode.US));
diff --git a/javascript/i18n/phonenumbers/phonenumberutil.js b/javascript/i18n/phonenumbers/phonenumberutil.js
index db90566a47..7cf61a9e18 100644
--- a/javascript/i18n/phonenumbers/phonenumberutil.js
+++ b/javascript/i18n/phonenumbers/phonenumberutil.js
@@ -784,8 +784,8 @@ i18n.phonenumbers.PhoneNumberUtil.ALPHANUM_ =
  * @private
  */
 i18n.phonenumbers.PhoneNumberUtil.RFC3966_DOMAINLABEL_ = '['
-    + i18n.phonenumbers.PhoneNumberUtil.ALPHANUM_ + ']+((\\-)*['
-    + i18n.phonenumbers.PhoneNumberUtil.ALPHANUM_ + '])*';
+    + i18n.phonenumbers.PhoneNumberUtil.ALPHANUM_ + ']+(\\-+['
+    + i18n.phonenumbers.PhoneNumberUtil.ALPHANUM_ + ']+)*';
 
 /**
  * @const
@@ -793,8 +793,8 @@ i18n.phonenumbers.PhoneNumberUtil.RFC3966_DOMAINLABEL_ = '['
  * @private
  */
 i18n.phonenumbers.PhoneNumberUtil.RFC3966_TOPLABEL_ = '['
-    + i18n.phonenumbers.PhoneNumberUtil.VALID_ALPHA_ + ']+((\\-)*['
-    + i18n.phonenumbers.PhoneNumberUtil.ALPHANUM_ + '])*';
+    + i18n.phonenumbers.PhoneNumberUtil.VALID_ALPHA_ + ']+(\\-+['
+    + i18n.phonenumbers.PhoneNumberUtil.ALPHANUM_ + ']+)*';
 
 /**
  * @const