diff --git a/.gitattributes b/.gitattributes
index 8830e8f..e08e0ce 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -6,5 +6,5 @@
 /www/ export-ignore
 /.gitattributes export-ignore
 /.gitignore export-ignore
+/TESTING.md export-ignore
 /TROUBLESHOOTING.md export-ignore
-/psalm.xml
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6153dad..738cf49 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -47,5 +47,5 @@ jobs:
           CI_PHP_FUTURE_RELEASE: ${{ matrix.future-release }}
 
       - name: Static analysis
-        run: "vendor/bin/psalm"
+        run: 'vendor/bin/psalm --config="tests/psalm.xml"'
         if: ${{ !matrix.future-release && matrix.php-version >= 7.1 }}
diff --git a/src/Curl/Url.php b/src/Curl/Url.php
index 125c4d6..a249d78 100644
--- a/src/Curl/Url.php
+++ b/src/Curl/Url.php
@@ -15,7 +15,7 @@ class Url
         $this->relativeUrl = $relative_url;
     }
 
-    public function __toString()
+    public function __toString() : string
     {
         return $this->absolutizeUrl();
     }
diff --git a/psalm.xml b/tests/psalm.xml
similarity index 78%
rename from psalm.xml
rename to tests/psalm.xml
index 94720bc..b163591 100644
--- a/psalm.xml
+++ b/tests/psalm.xml
@@ -7,20 +7,20 @@
     xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
 >
     <projectFiles>
-        <directory name="src" />
+        <directory name="../src" />
         <ignoreFiles>
-            <directory name="vendor" />
+            <directory name="../vendor" />
         </ignoreFiles>
     </projectFiles>
     <issueHandlers>
         <UndefinedClass>
             <errorLevel type="suppress">
                 <referencedClass name="CurlHandle" />
-                <file name="src/Curl/Curl.php" />
+                <file name="../src/Curl/Curl.php" />
             </errorLevel>
             <errorLevel type="suppress">
                 <referencedClass name="CurlMultiHandle" />
-                <file name="src/Curl/MultiCurl.php" />
+                <file name="../src/Curl/MultiCurl.php" />
             </errorLevel>
         </UndefinedClass>
     </issueHandlers>