diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 3c8d121..b33be25 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -1296,11 +1296,10 @@ function install_check_localization_server($uri) {
 /**
  * Gets the core release version and release alternatives for localization.
  *
- * In case core is a development version or the translation file for the release
- * is not available, fall back to the latest stable release. For example,
- * 8.2-dev might fall back to 8.1 and 8.0-dev might fall back to 7.0. Fallback
- * is required because the localization server only provides translation files
- * for stable releases.
+ * In case core is a development version or the translation file for the
+ * release is not available, fall back to an earlier release.
+ * For example, 8.2.0-dev might fall back to 8.1.0 and 8.0.0-dev
+ * might fall back to 7.0.
  *
  * @param string $version
  *   (optional) Version of core trying to find translation files for.
@@ -1308,90 +1307,83 @@ function install_check_localization_server($uri) {
  * @return array
  *   Array of release data. Each array element is an associative array with:
  *   - core: Core compatibility version (e.g., 8.x).
- *   - version: Release version (e.g., 8.1).
+ *   - version: Release version (e.g., 8.1.0).
  */
 function install_get_localization_release($version = \Drupal::VERSION) {
   $releases = array();
   $alternatives = array();
 
-  // The version string is broken up into:
-  // - major: Major version (e.g., "8").
-  // - minor: Minor version (e.g., "0").
-  // - extra: Extra version info (e.g., "alpha2").
-  // - extra_text: The text part of "extra" (e.g., "alpha").
-  // - extra_number: The number part of "extra" (e.g., "2").
   $info = _install_get_version_info($version);
 
+  // This code assumes there is a first alpha available as "alpha1". For
+  // Drupal 8.0.0 that isn't the case. In addition the semantic versioning
+  // wasn't introduced before "alpha14". However, we have already gotten to
+  // "beta1" so we are ignoring this for now.
+
+  // The fallback detection is relaxed - removing version duplicates at the end.
+
   // Check if the version is a regular stable release (no 'rc', 'beta', 'alpha',
   // 'dev', etc.)
   if (!isset($info['extra_text'])) {
     // First version alternative: the current version.
     $alternatives[] = $version;
-    // Point-releases: previous minor release (e.g., 8.2 falls back to 8.1).
-    if ($info['minor'] > 0) {
-      $alternatives[]= $info['major'] . '.' . ($info['minor'] - 1);
+
+    // Patch-level: Previous and zero patch level (e.g., 8.2.4 falls back to
+    // 8.2.3 and 8.2.0).
+    if ($info['patch'] > 0) {
+      $alternatives[] = $info['major'] . '.' . $info['minor'] . '.' . ($info['patch'] - 1);
+      $alternatives[] = $info['major'] . '.' . $info['minor'] . '.0';
     }
-    // Zero release: first release candidate (e.g., 8.0 falls back to 8.0-rc1).
+    // Zero patch: First release candidate (e.g., 8.0.0 falls back to
+    // 8.0.0-rc1).
     else {
-      $alternatives[] = $info['major'] . '.0-rc1';
+      $alternatives[] = $info['major'] . '.' . $info['minor'] . '.0-rc1';
+    }
+    // Point-releases: Previous and zero minor release (e.g., 8.2.x falls back
+    // to 8.1.0 and 8.0.0). Duplicates will be removed later.
+    if ($info['minor'] > 0) {
+      $alternatives[] = $info['major'] . '.' . ($info['minor'] - 1) . '.0';
+      $alternatives[] = $info['major'] . '.0.0';
     }
   }
   else {
-    switch ($info['extra_text']) {
-      // Alpha release: current alpha or previous alpha release (e.g. 8.0-alpha2
-      // falls back to 8.0-alpha1).
-      case 'alpha':
-        $alternatives[] = $version;
-        if ($info['extra_number'] > 1) {
-          $alternatives[] = $info['major'] . '.0-alpha' . ($info['extra_number'] - 1);
-        }
-        break;
-
-      // Beta release: current beta or previous beta release (e.g. 8.0-beta2
-      // falls back to 8.0-beta1) or first alpha release.
-      case 'beta':
-        $alternatives[] = $version;
-        if ($info['extra_number'] > 1) {
-          $alternatives[] = $info['major'] . '.0-beta' . ($info['extra_number'] - 1);
-        }
-        else {
-          $alternatives[] = $info['major'] . '.0-alpha2';
-        }
-        break;
-
-      // Dev release: the previous point release (e.g., 8.2-dev falls back to
-      // 8.1) or any unstable release (e.g., 8.0-dev falls back to 8.0-rc1,
-      // 8.0-beta1 or 8.0-alpha12)
-      case 'dev':
-        if ($info['minor'] >= 1) {
-          $alternatives[] = $info['major'] . '.' . ($info['minor'] - 1);
-        }
-        else {
-          $alternatives[] = $info['major'] . '.0-rc1';
-          $alternatives[] = $info['major'] . '.0-beta1';
-          $alternatives[] = $info['major'] . '.0-alpha12';
-        }
-        break;
-
-      // Release candidate: the current or previous release candidate (e.g.,
-      // 8.0-rc2 falls back to 8.0-rc1) or the first beta release.
-      case 'rc':
-        $alternatives[] =  $version;
-        if ($info['extra_number'] >= 2) {
-          $alternatives[] = $info['major'] . '.0-rc' . ($info['extra_number'] - 1);
-        }
-        else {
-          $alternatives[] = $info['major'] . '.0-beta1';
-        }
-        break;
+    // Below we assume that for all dev, alpha, beta or rc releases
+    // the patch level is 0.
+
+    $release_levels = array('rc', 'beta', 'alpha');
+
+    if ($info['extra_text'] == 'dev') {
+      // Dev release: Any unstable release (e.g., 8.2.0-dev falls back to
+      // 8.2.0-rc1, 8.2.0-beta1 and 8.2.0-alpha1).
+      $alternatives[] = $info['major'] . '.' . $info['minor'] . '.0-rc1';
+      $alternatives[] = $info['major'] . '.' . $info['minor'] . '.0-beta1';
+      $alternatives[] = $info['major'] . '.' . $info['minor'] . '.0-alpha1';
+    } elseif (in_array($info['extra_text'], $release_levels)) {
+      // All other unstable release always includes the current version
+      $alternatives[] = $version;
+      // Alpha release: Previous alpha release (e.g. 8.0.0-alpha2 falls back
+      // to 8.0.0-alpha1).
+      // Beta release: Previous beta release and first alpha release (e.g.
+      // 8.0.0-beta2 falls back to 8.0.0-beta1 and 8.0.0-alpha1).
+      // Release candidate: Previous release candidate and the first beta
+      // release (e.g. 8.0.0-rc2 falls back to 8.0.0-rc1 and 8.0.0-beta1).
+      $release_level_key = array_search($info['extra_text'], $release_levels);
+      if ($info['extra_number'] > 1) {
+        $alternatives[] = $info['major'] . '.' . $info['minor'] . '.0-' . $info['extra_text'] . ($info['extra_number'] - 1);
+      }
+      if ($info['extra_text'] != 'alpha') {
+        $alternatives[] = $info['major'] . '.' . $info['minor'] . '.0-' . $release_levels[$release_level_key + 1] . '1';
+      }
+    }
+    // All unstable releases except the zero release: The previous minor release
+    // and the zero release. Duplicates will be removed later.
+    if ($info['minor'] > 0) {
+      $alternatives[] = $info['major'] . '.' . ($info['minor'] - 1) . '.0';
+      $alternatives[] = $info['major'] . '.0.0';
     }
   }
 
-  // All releases may fall back to the previous major release (e.g., 8.1 falls
-  // back to 7.0, 8.x-dev falls back to 7.0). This will probably only be used
-  // for early dev releases or languages with an inactive translation team.
-  $alternatives[] = $info['major'] - 1 . '.0';
-
+  $alternatives = array_unique($alternatives);
   foreach ($alternatives as $alternative) {
     list($core) = explode('.', $alternative);
     $releases[] = array(
@@ -1400,6 +1392,23 @@ function install_get_localization_release($version = \Drupal::VERSION) {
     );
   }
 
+  // All releases may fall back to the previous major release (e.g., 8.1.0
+  // may fall back to 7.0). This will probably only be used for early dev
+  // releases or languages with an inactive translation team.
+  if ($info['major'] == 8) {
+    $releases[] = array(
+      'core' => '7.x',
+      'version' => '7.0',
+    );
+  }
+  else {
+    $prev_major = $info['major'] - 1;
+    $releases[] = array(
+      'core' => $prev_major . '.x',
+      'version' => $prev_major . '.0.0',
+    );
+  }
+
   return $releases;
 }
 
@@ -1407,14 +1416,14 @@ function install_get_localization_release($version = \Drupal::VERSION) {
  * Extracts version information from a drupal core version string.
  *
  * @param string $version
- *   Version info string (e.g., 8.0, 8.1, 8.0-dev, 8.0-unstable1, 8.0-alpha2,
- *   8.0-beta3, and 8.0-rc4).
- *
+ *   Version info string (e.g., 8.0.0, 8.1.0, 8.0.0-dev, 8.0.0-unstable1,
+ *   8.0.0-alpha2, 8.0.0-beta3, and 8.0.0-rc4).
  *
  * @return array
  *   Associative array of version info:
  *   - major: Major version (e.g., "8").
  *   - minor: Minor version (e.g., "0").
+ *   - patch: Patch version (e.g., "0").
  *   - extra: Extra version info (e.g., "alpha2").
  *   - extra_text: The text part of "extra" (e.g., "alpha").
  *   - extra_number: The number part of "extra" (e.g., "2").
@@ -1425,6 +1434,8 @@ function _install_get_version_info($version) {
       (?P<major>[0-9]+)    # Major release number.
       \.          # .
       (?P<minor>[0-9]+)    # Minor release number.
+      \.          # .
+      (?P<patch>[0-9]+)    # Patch release number.
     )             #
     (             #
       -           # - separator for "extra" version information.
diff --git a/core/modules/system/src/Tests/Installer/InstallerTranslationVersionUnitTest.php b/core/modules/system/src/Tests/Installer/InstallerTranslationVersionUnitTest.php
index 031a79d..2334533 100644
--- a/core/modules/system/src/Tests/Installer/InstallerTranslationVersionUnitTest.php
+++ b/core/modules/system/src/Tests/Installer/InstallerTranslationVersionUnitTest.php
@@ -62,56 +62,99 @@ protected function assertVersionFallback($version, $fallback, $message = '', $gr
    * Tests version fallback of install_get_localization_release().
    */
   public function testVersionFallback() {
-    $version = '8.0';
-    $fallback = array('8.0', '8.0-rc1', '7.0');
+    $version = '8.0.0';
+    $fallback = array('8.0.0', '8.0.0-rc1', '7.0');
     $this->assertVersionFallback($version, $fallback);
 
-    $version = '8.1';
-    $fallback = array('8.1', '8.0', '7.0');
+    $version = '8.1.0';
+    $fallback = array('8.1.0', '8.1.0-rc1', '8.0.0', '7.0');
     $this->assertVersionFallback($version, $fallback);
 
-    $version = '8.12';
-    $fallback = array('8.12', '8.11', '7.0');
+    $version = '8.12.0';
+    $fallback = array('8.12.0', '8.12.0-rc1', '8.11.0', '8.0.0', '7.0');
     $this->assertVersionFallback($version, $fallback);
 
-    $version = '8.0-dev';
-    $fallback = array('8.0-rc1', '8.0-beta1', '8.0-alpha12', '7.0');
+    $version = '8.0.0-dev';
+    $fallback = array('8.0.0-rc1', '8.0.0-beta1', '8.0.0-alpha1', '7.0');
     $this->assertVersionFallback($version, $fallback);
 
-    $version = '8.9-dev';
-    $fallback = array('8.8', '7.0');
+    $version = '8.9.0-dev';
+    $fallback = array();
+    $fallback = array(
+      '8.9.0-rc1',
+      '8.9.0-beta1',
+      '8.9.0-alpha1',
+      '8.8.0',
+      '8.0.0',
+      '7.0'
+    );
     $this->assertVersionFallback($version, $fallback);
 
-    $version = '8.0-alpha3';
-    $fallback = array('8.0-alpha3', '8.0-alpha2', '7.0');
+    $version = '8.0.0-alpha3';
+    $fallback = array('8.0.0-alpha3', '8.0.0-alpha2', '7.0');
     $this->assertVersionFallback($version, $fallback);
 
-    $version = '8.0-alpha1';
-    $fallback = array('8.0-alpha1', '7.0');
+    $version = '8.0.0-alpha1';
+    $fallback = array('8.0.0-alpha1', '7.0');
     $this->assertVersionFallback($version, $fallback);
 
-    $version = '8.0-beta2';
-    $fallback = array('8.0-beta2', '8.0-beta1', '7.0');
+    $version = '8.0.0-beta2';
+    $fallback = array('8.0.0-beta2', '8.0.0-beta1', '8.0.0-alpha1', '7.0');
     $this->assertVersionFallback($version, $fallback);
 
-    $version = '8.0-beta1';
-    $fallback = array('8.0-beta1', '8.0-alpha2', '7.0');
+    $version = '8.0.0-beta1';
+    $fallback = array('8.0.0-beta1', '8.0.0-alpha1', '7.0');
     $this->assertVersionFallback($version, $fallback);
 
-    $version = '8.0-rc8';
-    $fallback = array('8.0-rc8', '8.0-rc7', '7.0');
+    $version = '8.0.0-rc8';
+    $fallback = array('8.0.0-rc8', '8.0.0-rc7', '8.0.0-beta1', '7.0');
     $this->assertVersionFallback($version, $fallback);
 
-    $version = '8.0-rc1';
-    $fallback = array('8.0-rc1', '8.0-beta1', '7.0');
+    $version = '8.0.0-rc1';
+    $fallback = array('8.0.0-rc1', '8.0.0-beta1', '7.0');
     $this->assertVersionFallback($version, $fallback);
 
-    $version = '8.0-foo2';
+    $version = '8.2.0-beta1';
+    $fallback = array('8.2.0-beta1', '8.2.0-alpha1', '8.1.0', '8.0.0', '7.0');
+    $this->assertVersionFallback($version, $fallback);
+
+    $version = '8.2.0-beta7';
+    $fallback = array('8.2.0-beta7', '8.2.0-beta6', '8.2.0-alpha1', '8.1.0', '8.0.0', '7.0');
+    $this->assertVersionFallback($version, $fallback);
+
+    $version = '8.2.0-rc1';
+    $fallback = array('8.2.0-rc1', '8.2.0-beta1', '8.1.0', '8.0.0', '7.0');
+    $this->assertVersionFallback($version, $fallback);
+
+    $version = '8.2.0-rc2';
+    $fallback = array(
+      '8.2.0-rc2',
+      '8.2.0-rc1',
+      '8.2.0-beta1',
+      '8.1.0',
+      '8.0.0',
+      '7.0',
+    );
+    $this->assertVersionFallback($version, $fallback);
+
+    $version = '8.0.0-foo2';
     $fallback = array('7.0');
     $this->assertVersionFallback($version, $fallback);
 
-    $version = '99.2';
-    $fallback = array('99.2', '99.1', '98.0');
+    $version = '8.0.4';
+    $fallback = array('8.0.4', '8.0.3', '8.0.0', '7.0');
+    $this->assertVersionFallback($version, $fallback);
+
+    $version = '8.3.5';
+    $fallback = array('8.3.5', '8.3.4', '8.3.0', '8.2.0', '8.0.0', '7.0');
+    $this->assertVersionFallback($version, $fallback);
+
+    $version = '99.0.1';
+    $fallback = array('99.0.1', '99.0.0' ,'98.0.0');
+    $this->assertVersionFallback($version, $fallback);
+
+    $version = '99.7.1';
+    $fallback = array('99.7.1', '99.7.0', '99.6.0', '99.0.0' ,'98.0.0');
     $this->assertVersionFallback($version, $fallback);
   }
 }