diff --git a/JaegerBaggagePropagator.php b/JaegerBaggagePropagator.php
index a7a2b6c..dd53b22 100644
--- a/JaegerBaggagePropagator.php
+++ b/JaegerBaggagePropagator.php
@@ -39,7 +39,7 @@ public function fields(): array
     }
 
     /** {@inheritdoc} */
-    public function inject(&$carrier, PropagationSetterInterface $setter = null, ContextInterface $context = null): void
+    public function inject(&$carrier, ?PropagationSetterInterface $setter = null, ?ContextInterface $context = null): void
     {
         $setter ??= ArrayAccessGetterSetter::getInstance();
         $context ??= Context::getCurrent();
@@ -59,7 +59,7 @@ public function inject(&$carrier, PropagationSetterInterface $setter = null, Con
     }
 
     /** {@inheritdoc} */
-    public function extract($carrier, PropagationGetterInterface $getter = null, ContextInterface $context = null): ContextInterface
+    public function extract($carrier, ?PropagationGetterInterface $getter = null, ?ContextInterface $context = null): ContextInterface
     {
         $getter ??= ArrayAccessGetterSetter::getInstance();
         $context ??= Context::getCurrent();
diff --git a/JaegerPropagator.php b/JaegerPropagator.php
index 3064c57..31cdcd5 100644
--- a/JaegerPropagator.php
+++ b/JaegerPropagator.php
@@ -51,7 +51,7 @@ public function fields(): array
     }
 
     /** {@inheritdoc} */
-    public function inject(&$carrier, PropagationSetterInterface $setter = null, ContextInterface $context = null): void
+    public function inject(&$carrier, ?PropagationSetterInterface $setter = null, ?ContextInterface $context = null): void
     {
         $setter ??= ArrayAccessGetterSetter::getInstance();
         $context ??= Context::getCurrent();
@@ -75,7 +75,7 @@ public function inject(&$carrier, PropagationSetterInterface $setter = null, Con
     }
 
     /** {@inheritdoc} */
-    public function extract($carrier, PropagationGetterInterface $getter = null, ContextInterface $context = null): ContextInterface
+    public function extract($carrier, ?PropagationGetterInterface $getter = null, ?ContextInterface $context = null): ContextInterface
     {
         $getter ??= ArrayAccessGetterSetter::getInstance();
         $context ??= Context::getCurrent();