diff --git a/composer.json b/composer.json
index 5f3a49e17..7fdb2a2c5 100644
--- a/composer.json
+++ b/composer.json
@@ -32,7 +32,8 @@
         "ext-json": "*",
         "guzzlehttp/promises": "^1.4",
         "guzzlehttp/psr7": "^1.7 || ^2.0",
-        "psr/http-client": "^1.0"
+        "psr/http-client": "^1.0",
+        "symfony/deprecation-contracts": "^2.2"
     },
     "provide": {
         "psr/http-client-implementation": "1.0"
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 8ada6052b..a3bd3376e 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -110,3 +110,7 @@ parameters:
 			count: 2
 			path: src/Middleware.php
 
+		-
+			message: "#^Result of && is always false\\.$#"
+			count: 1
+			path: src/Cookie/SetCookie.php
diff --git a/src/Cookie/SetCookie.php b/src/Cookie/SetCookie.php
index 602370d6f..e3bafef9d 100644
--- a/src/Cookie/SetCookie.php
+++ b/src/Cookie/SetCookie.php
@@ -128,6 +128,10 @@ public function getName()
      */
     public function setName($name): void
     {
+        if (!is_string($name)) {
+            trigger_deprecation('guzzlehttp/guzzle', '7.4', 'Not passing a string to %s::%s() is deprecated and will cause an error in 8.0.', __CLASS__, __FUNCTION__);
+        }
+
         $this->data['Name'] = $name;
     }
 
@@ -148,6 +152,10 @@ public function getValue()
      */
     public function setValue($value): void
     {
+        if (!is_string($value)) {
+            trigger_deprecation('guzzlehttp/guzzle', '7.4', 'Not passing a string to %s::%s() is deprecated and will cause an error in 8.0.', __CLASS__, __FUNCTION__);
+        }
+
         $this->data['Value'] = $value;
     }
 
@@ -168,6 +176,10 @@ public function getDomain()
      */
     public function setDomain($domain): void
     {
+        if (!is_string($domain)) {
+            trigger_deprecation('guzzlehttp/guzzle', '7.4', 'Not passing a string to %s::%s() is deprecated and will cause an error in 8.0.', __CLASS__, __FUNCTION__);
+        }
+
         $this->data['Domain'] = $domain;
     }
 
@@ -188,6 +200,10 @@ public function getPath()
      */
     public function setPath($path): void
     {
+        if (!is_string($path)) {
+            trigger_deprecation('guzzlehttp/guzzle', '7.4', 'Not passing a string to %s::%s() is deprecated and will cause an error in 8.0.', __CLASS__, __FUNCTION__);
+        }
+
         $this->data['Path'] = $path;
     }
 
@@ -198,7 +214,7 @@ public function setPath($path): void
      */
     public function getMaxAge()
     {
-        return $this->data['Max-Age'];
+        return null === $this->data['Max-Age'] ? null : (int) $this->data['Max-Age'];
     }
 
     /**
@@ -208,6 +224,10 @@ public function getMaxAge()
      */
     public function setMaxAge($maxAge): void
     {
+        if (!is_int($maxAge)) {
+            trigger_deprecation('guzzlehttp/guzzle', '7.4', 'Not passing an int to %s::%s() is deprecated and will cause an error in 8.0.', __CLASS__, __FUNCTION__);
+        }
+
         $this->data['Max-Age'] = $maxAge;
     }
 
@@ -228,6 +248,10 @@ public function getExpires()
      */
     public function setExpires($timestamp): void
     {
+        if (!is_int($timestamp) && !is_string($timestamp)) {
+            trigger_deprecation('guzzlehttp/guzzle', '7.4', 'Not passing an int or string to %s::%s() is deprecated and will cause an error in 8.0.', __CLASS__, __FUNCTION__);
+        }
+
         $this->data['Expires'] = \is_numeric($timestamp)
             ? (int) $timestamp
             : \strtotime($timestamp);
@@ -250,6 +274,10 @@ public function getSecure()
      */
     public function setSecure($secure): void
     {
+        if (!is_bool($secure)) {
+            trigger_deprecation('guzzlehttp/guzzle', '7.4', 'Not passing a boolean to %s::%s() is deprecated and will cause an error in 8.0.', __CLASS__, __FUNCTION__);
+        }
+
         $this->data['Secure'] = $secure;
     }
 
@@ -270,6 +298,10 @@ public function getDiscard()
      */
     public function setDiscard($discard): void
     {
+        if (!is_bool($discard)) {
+            trigger_deprecation('guzzlehttp/guzzle', '7.4', 'Not passing a boolean to %s::%s() is deprecated and will cause an error in 8.0.', __CLASS__, __FUNCTION__);
+        }
+
         $this->data['Discard'] = $discard;
     }
 
@@ -290,6 +322,10 @@ public function getHttpOnly()
      */
     public function setHttpOnly($httpOnly): void
     {
+        if (!is_bool($httpOnly)) {
+            trigger_deprecation('guzzlehttp/guzzle', '7.4', 'Not passing a boolean to %s::%s() is deprecated and will cause an error in 8.0.', __CLASS__, __FUNCTION__);
+        }
+
         $this->data['HttpOnly'] = $httpOnly;
     }