diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index ca78c847b32..2c3b93c64d4 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -1,3 +1,7 @@
+Drupal 7.77, 2020-12-03
+-----------------------
+- Hotfix for schema.prefixed tables
+
 Drupal 7.76, 2020-12-02
 -----------------------
 - Support for MySQL 8
diff --git a/includes/bootstrap.inc b/includes/bootstrap.inc
index f862144e4f5..cb70533e46a 100644
--- a/includes/bootstrap.inc
+++ b/includes/bootstrap.inc
@@ -8,7 +8,7 @@
 /**
  * The current system version.
  */
-define('VERSION', '7.76');
+define('VERSION', '7.77');
 
 /**
  * Core API compatibility.
diff --git a/includes/database/mysql/database.inc b/includes/database/mysql/database.inc
index af12c57e0de..00df3c13e91 100644
--- a/includes/database/mysql/database.inc
+++ b/includes/database/mysql/database.inc
@@ -392,8 +392,11 @@ class DatabaseConnection_mysql extends DatabaseConnection {
       if (substr($prefixSearch, 0, 1) === '{') {
         // If the prefix already contains one or more quotes remove them.
         // This can happen when - for example - DrupalUnitTestCase sets up a
-        // "temporary prefixed database".
-        $this->prefixReplace[$i] = $quote_char . str_replace($quote_char, '', $this->prefixReplace[$i]);
+        // "temporary prefixed database". Also if there's a dot in the prefix,
+        // wrap it in quotes to cater for schema names in prefixes.
+        $search = array($quote_char, '.');
+        $replace = array('', $quote_char . '.' . $quote_char);
+        $this->prefixReplace[$i] = $quote_char . str_replace($search, $replace, $this->prefixReplace[$i]);
       }
       if (substr($prefixSearch, -1) === '}') {
         $this->prefixReplace[$i] .= $quote_char;
diff --git a/modules/simpletest/tests/database_test.test b/modules/simpletest/tests/database_test.test
index dca8168f0a6..04be5c85b84 100644
--- a/modules/simpletest/tests/database_test.test
+++ b/modules/simpletest/tests/database_test.test
@@ -4247,9 +4247,9 @@ class ConnectionUnitTest extends DrupalUnitTestCase {
   }
 }
 
-  /**
-   * Test reserved keyword handling (introduced for MySQL 8+)
-   */
+/**
+ * Test reserved keyword handling (introduced for MySQL 8+)
+*/
 class DatabaseReservedKeywordTestCase extends DatabaseTestCase {
   public static function getInfo() {
     return array(
@@ -4373,5 +4373,50 @@ class DatabaseReservedKeywordTestCase extends DatabaseTestCase {
     $num_records_after = db_query('SELECT COUNT(*) FROM {virtual}')->fetchField();
     $this->assertIdentical($num_records_before, $num_records_after, 'Successful merge query on a table with a name and column which are reserved words.');
   }
+}
+
+/**
+ * Test table prefix handling.
+*/
+class DatabaseTablePrefixTestCase extends DatabaseTestCase {
+  public static function getInfo() {
+    return array(
+      'name' => 'Table prefixes',
+      'description' => 'Test handling of table prefixes.',
+      'group' => 'Database',
+    );
+  }
 
+  public function testSchemaDotTablePrefixes() {
+    // Get a copy of the default connection options.
+    $db = Database::getConnection('default', 'default');
+    $connection_options = $db->getConnectionOptions();
+
+    if ($connection_options['driver'] === 'sqlite') {
+      // In SQLite simpletest's prefixed db tables exist in their own schema
+      // (e.g. simpletest124904.system), so we cannot test the schema.table
+      // prefix syntax here.
+      $this->assert(TRUE, 'Skipping schema.table prefixed tables test for SQLite.');
+      return;
+    }
+
+    $db_name = $connection_options['database'];
+    // This prefix is usually something like simpletest12345
+    $test_prefix = $connection_options['prefix']['default'];
+
+    // Set up a new connection with table prefixes in the form "schema.table"
+    $prefixed = $connection_options;
+    $prefixed['prefix'] = array(
+      'default' => $test_prefix,
+      'users' => $db_name . '.' . $test_prefix,
+      'role' => $db_name . '.' . $test_prefix,
+    );
+    Database::addConnectionInfo('default', 'prefixed', $prefixed);
+
+    // Test that the prefixed database connection can query the prefixed tables.
+    $num_users_prefixed = Database::getConnection('prefixed', 'default')->query('SELECT COUNT(1) FROM {users}')->fetchField();
+    $this->assertTrue((int) $num_users_prefixed > 0, 'Successfully queried the users table using a schema.table prefix');
+    $num_users_default = Database::getConnection('default', 'default')->query('SELECT COUNT(1) FROM {users}')->fetchField();
+    $this->assertEqual($num_users_default, $num_users_prefixed, 'Verified results of query using a connection with schema.table prefixed tables');
+  }
 }