diff --git a/cpp/src/phonenumbers/phonenumbermatcher.cc b/cpp/src/phonenumbers/phonenumbermatcher.cc
index 794c3c682e..87e99004cb 100644
--- a/cpp/src/phonenumbers/phonenumbermatcher.cc
+++ b/cpp/src/phonenumbers/phonenumbermatcher.cc
@@ -123,7 +123,10 @@ bool AllNumberGroupsRemainGrouped(
   if (number.country_code_source() != PhoneNumber::FROM_DEFAULT_COUNTRY) {
     // First skip the country code if the normalized candidate contained it.
     string country_code = SimpleItoa(number.country_code());
-    from_index = normalized_candidate.find(country_code) + country_code.size();
+    size_t country_code_index = normalized_candidate.find(country_code);
+    if (country_code_index != string::npos) {
+      from_index = country_code_index + country_code.size();
+    }
   }
   // Check each group of consecutive digits are not broken into separate
   // groupings in the normalized_candidate string.
diff --git a/java/libphonenumber/src/com/google/i18n/phonenumbers/PhoneNumberMatcher.java b/java/libphonenumber/src/com/google/i18n/phonenumbers/PhoneNumberMatcher.java
index b812551db0..0d130edf01 100644
--- a/java/libphonenumber/src/com/google/i18n/phonenumbers/PhoneNumberMatcher.java
+++ b/java/libphonenumber/src/com/google/i18n/phonenumbers/PhoneNumberMatcher.java
@@ -463,7 +463,10 @@ static boolean allNumberGroupsRemainGrouped(PhoneNumberUtil util,
     if (number.getCountryCodeSource() != CountryCodeSource.FROM_DEFAULT_COUNTRY) {
       // First skip the country code if the normalized candidate contained it.
       String countryCode = Integer.toString(number.getCountryCode());
-      fromIndex = normalizedCandidate.indexOf(countryCode) + countryCode.length();
+      int countryCodeIndex = normalizedCandidate.indexOf(countryCode);
+      if (countryCodeIndex >= 0) {
+        fromIndex = countryCodeIndex + countryCode.length();
+      }
     }
     // Check each group of consecutive digits are not broken into separate groupings in the
     // {@code normalizedCandidate} string.
diff --git a/java/libphonenumber/test/com/google/i18n/phonenumbers/PhoneNumberMatcherTest.java b/java/libphonenumber/test/com/google/i18n/phonenumbers/PhoneNumberMatcherTest.java
index d31b33951b..a00255014d 100644
--- a/java/libphonenumber/test/com/google/i18n/phonenumbers/PhoneNumberMatcherTest.java
+++ b/java/libphonenumber/test/com/google/i18n/phonenumbers/PhoneNumberMatcherTest.java
@@ -77,6 +77,21 @@ public void testContainsMoreThanOneSlashInNationalNumber() throws Exception {
     assertTrue(PhoneNumberMatcher.containsMoreThanOneSlashInNationalNumber(number, candidate));
   }
 
+  public void testAllNumberGroupsRemainGroupedCountryCodeNotInCandidate() throws Exception {
+    // Constructed case: the country code source claims the candidate began with an explicit
+    // country calling code, but the literal digits of that code ("44") do not actually occur in
+    // the candidate text. Previously this desynced fromIndex (indexOf returns -1, and -1 plus the
+    // country code's length was used as a starting position instead of being treated as "not
+    // found"), which made a grouping match that should succeed incorrectly return false.
+    PhoneNumber number = new PhoneNumber();
+    number.setCountryCode(44);
+    number.setCountryCodeSource(CountryCodeSource.FROM_NUMBER_WITH_PLUS_SIGN);
+    StringBuilder candidate = new StringBuilder("020 7031 3000");
+    String[] formattedNumberGroups = {"020", "7031", "3000"};
+    assertTrue(PhoneNumberMatcher.allNumberGroupsRemainGrouped(
+        phoneUtil, number, candidate, formattedNumberGroups));
+  }
+
   /** See {@link PhoneNumberUtilTest#testParseNationalNumber()}. */
   public void testFindNationalNumber() throws Exception {
     // same cases as in testParseNationalNumber