diff --git a/src/AbstractManifest.php b/src/AbstractManifest.php
index 4c5cd2a..653f0d6 100644
--- a/src/AbstractManifest.php
+++ b/src/AbstractManifest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools;
 
 use Normalizer;
diff --git a/src/Bag.php b/src/Bag.php
index b455f02..0c97359 100644
--- a/src/Bag.php
+++ b/src/Bag.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools;
 
 use Archive_Tar;
diff --git a/src/BagUtils.php b/src/BagUtils.php
index 26e4595..d1f217a 100644
--- a/src/BagUtils.php
+++ b/src/BagUtils.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools;
 
 use TypeError;
@@ -413,7 +415,7 @@ public static function encodeFilepath(string $line): string
      */
     public static function checkUnencodedFilepath(string $filepath): bool
     {
-        return preg_match_all("/%(?!(25|0A|0D))/", $filepath);
+        return (bool) preg_match_all("/%(?!(25|0A|0D))/", $filepath);
     }
 
     /**
diff --git a/src/Commands/ValidateCommand.php b/src/Commands/ValidateCommand.php
index 65a32bf..38aec18 100644
--- a/src/Commands/ValidateCommand.php
+++ b/src/Commands/ValidateCommand.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools\Commands;
 
 use Symfony\Component\Console\Command\Command;
diff --git a/src/Exceptions/BagItException.php b/src/Exceptions/BagItException.php
index 535ea90..f62927f 100644
--- a/src/Exceptions/BagItException.php
+++ b/src/Exceptions/BagItException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/FilesystemException.php b/src/Exceptions/FilesystemException.php
index 8400a6b..ce9bf52 100644
--- a/src/Exceptions/FilesystemException.php
+++ b/src/Exceptions/FilesystemException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools\Exceptions;
 
 /**
diff --git a/src/Fetch.php b/src/Fetch.php
index 73fd68f..7d841bf 100644
--- a/src/Fetch.php
+++ b/src/Fetch.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools;
 
 use Normalizer;
diff --git a/src/PayloadManifest.php b/src/PayloadManifest.php
index 05c1d0b..26d9a88 100644
--- a/src/PayloadManifest.php
+++ b/src/PayloadManifest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools;
 
 /**
@@ -11,16 +13,18 @@
  */
 class PayloadManifest extends AbstractManifest
 {
-  /**
-   * PayloadManifest constructor.
-   *
-   * @param \whikloj\BagItTools\Bag $bag
-   *   The bag this manifest is part of.
-   * @param string $algorithm
-   *   The BagIt name of the hash algorithm.
-   * @param bool $load
-   *   Whether we are loading an existing file
-   */
+    /**
+     * PayloadManifest constructor.
+     *
+     * @param \whikloj\BagItTools\Bag $bag
+     *   The bag this manifest is part of.
+     * @param string $algorithm
+     *   The BagIt name of the hash algorithm.
+     * @param bool $load
+     *   Whether we are loading an existing file
+     * @throws \whikloj\BagItTools\Exceptions\FilesystemException
+     *   Unable to read manifest file.
+     */
     public function __construct(Bag $bag, string $algorithm, bool $load = false)
     {
         parent::__construct($bag, $algorithm, "manifest-$algorithm.txt", $load);
diff --git a/src/TagManifest.php b/src/TagManifest.php
index b449ff0..41a6787 100644
--- a/src/TagManifest.php
+++ b/src/TagManifest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools;
 
 /**
@@ -11,16 +13,18 @@
  */
 class TagManifest extends AbstractManifest
 {
-  /**
-   * PayloadManifest constructor.
-   *
-   * @param \whikloj\BagItTools\Bag $bag
-   *   The bag this manifest is part of.
-   * @param string $algorithm
-   *   The BagIt name of the hash algorithm.
-   * @param boolean $load
-   *   Whether we are loading an existing file
-   */
+    /**
+     * PayloadManifest constructor.
+     *
+     * @param \whikloj\BagItTools\Bag $bag
+     *   The bag this manifest is part of.
+     * @param string $algorithm
+     *   The BagIt name of the hash algorithm.
+     * @param boolean $load
+     *   Whether we are loading an existing file
+     * @throws \whikloj\BagItTools\Exceptions\FilesystemException
+     *   Unable to read manifest file.
+     */
     public function __construct(Bag $bag, string $algorithm, bool $load = false)
     {
         parent::__construct($bag, $algorithm, "tagmanifest-$algorithm.txt", $load);
diff --git a/tests/BagInternalTest.php b/tests/BagInternalTest.php
index a72f3bb..a219946 100644
--- a/tests/BagInternalTest.php
+++ b/tests/BagInternalTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools\Test;
 
 use ReflectionClass;
diff --git a/tests/BagItTestFramework.php b/tests/BagItTestFramework.php
index 581e86b..52f77d9 100644
--- a/tests/BagItTestFramework.php
+++ b/tests/BagItTestFramework.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools\Test;
 
 use PHPUnit\Framework\TestCase;
diff --git a/tests/BagTest.php b/tests/BagTest.php
index 13ebf3c..d3c7698 100644
--- a/tests/BagTest.php
+++ b/tests/BagTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools\Test;
 
 use whikloj\BagItTools\Bag;
@@ -823,7 +825,7 @@ public function testUpdateV07(): void
         $this->assertTrue($bag->validate());
         $fp = fopen($bag->getBagRoot() . DIRECTORY_SEPARATOR . 'bag-info.txt', 'r');
         while (!feof($fp)) {
-            $line = fgets($fp);
+            $line = (string) fgets($fp);
             $line = trim($line);
             if (empty($line)) {
                 continue;
@@ -837,7 +839,7 @@ public function testUpdateV07(): void
         $this->assertTrue($bag->validate());
         $fp = fopen($bag->getBagRoot() . DIRECTORY_SEPARATOR . 'bag-info.txt', 'r');
         while (!feof($fp)) {
-            $line = fgets($fp);
+            $line = (string) fgets($fp);
             $line = trim($line);
             if (empty($line)) {
                 continue;
diff --git a/tests/BagUtilsTest.php b/tests/BagUtilsTest.php
index 9535808..b1d19fe 100644
--- a/tests/BagUtilsTest.php
+++ b/tests/BagUtilsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools\Test;
 
 use Exception;
diff --git a/tests/CommandTest.php b/tests/CommandTest.php
index 7a0b268..77c3b5e 100644
--- a/tests/CommandTest.php
+++ b/tests/CommandTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools\Test;
 
 use Symfony\Component\Console\Application;
diff --git a/tests/ExtendedBagTest.php b/tests/ExtendedBagTest.php
index 34c7b4d..f40657b 100644
--- a/tests/ExtendedBagTest.php
+++ b/tests/ExtendedBagTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools\Test;
 
 use whikloj\BagItTools\Bag;
diff --git a/tests/FetchTest.php b/tests/FetchTest.php
index 6ebc1c2..a1f51b2 100644
--- a/tests/FetchTest.php
+++ b/tests/FetchTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools\Test;
 
 use donatj\MockWebServer\MockWebServer;
diff --git a/tests/ManifestTest.php b/tests/ManifestTest.php
index c74ea4b..74e4213 100644
--- a/tests/ManifestTest.php
+++ b/tests/ManifestTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace whikloj\BagItTools\Test;
 
 use whikloj\BagItTools\Bag;