diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 21bdbe4..e7e8566 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -30,10 +30,16 @@ jobs:
           php-version: ${{ matrix.php }}
           coverage: xdebug
       - run: composer install
-      - run: vendor/bin/phpunit --coverage-text
+      - run: vendor/bin/phpunit --coverage-text --coverage-clover=clover.xml
         if: ${{ matrix.php >= 7.3 }}
-      - run: vendor/bin/phpunit --coverage-text -c phpunit.xml.legacy
+      - run: vendor/bin/phpunit --coverage-text --coverage-clover=clover.xml -c phpunit.xml.legacy
         if: ${{ matrix.php < 7.3 }}
+      - name: Check 100% code coverage
+        shell: php {0}
+        run: |
+          <?php
+          $metrics = simplexml_load_file('clover.xml')->project->metrics;
+          exit((int) $metrics['statements'] === (int) $metrics['coveredstatements'] ? 0 : 1);
 
   PHPUnit-hhvm:
     name: PHPUnit (HHVM)
diff --git a/src/Decoder.php b/src/Decoder.php
index 9ef99a3..876ff2b 100644
--- a/src/Decoder.php
+++ b/src/Decoder.php
@@ -113,11 +113,14 @@ public function handleData($data)
             $this->buffer = (string)\substr($this->buffer, $newline + 1);
 
             // decode data with options given in ctor
+            // @codeCoverageIgnoreStart
             if ($this->options === 0) {
                 $data = \json_decode($data, $this->assoc, $this->depth);
             } else {
+                assert(\PHP_VERSION_ID >= 50400);
                 $data = \json_decode($data, $this->assoc, $this->depth, $this->options);
             }
+            // @codeCoverageIgnoreEnd
 
             // abort stream if decoding failed
             if ($data === null && \json_last_error() !== \JSON_ERROR_NONE) {