diff --git a/src/Attributes/Attribute.php b/src/Attributes/Attribute.php
index 3a79c84c5..56820e483 100644
--- a/src/Attributes/Attribute.php
+++ b/src/Attributes/Attribute.php
@@ -9,7 +9,7 @@
 
 /**
  * @phpstan-type AttributeType 'string'|'boolean'|'integer'|'double'
- * @phpstan-type AttributeValue string|bool|int|float
+ * @phpstan-type AttributeValue string|bool|int|float|null
  */
 class Attribute
 {
diff --git a/src/Metrics/MetricsAggregator.php b/src/Metrics/MetricsAggregator.php
index a4a3aef3e..d946ca35a 100644
--- a/src/Metrics/MetricsAggregator.php
+++ b/src/Metrics/MetricsAggregator.php
@@ -41,8 +41,8 @@ final class MetricsAggregator
     private $metrics;
 
     /**
-     * @param int|float                            $value
-     * @param array<string, int|float|string|bool> $attributes
+     * @param int|float                                 $value
+     * @param array<string, int|float|string|bool|null> $attributes
      */
     public function add(
         string $type,
diff --git a/src/Metrics/TraceMetrics.php b/src/Metrics/TraceMetrics.php
index 4eae90d38..4fa9aa927 100644
--- a/src/Metrics/TraceMetrics.php
+++ b/src/Metrics/TraceMetrics.php
@@ -32,8 +32,8 @@ public static function getInstance(): self
     }
 
     /**
-     * @param int|float                            $value
-     * @param array<string, int|float|string|bool> $attributes
+     * @param int|float                                 $value
+     * @param array<string, int|float|string|bool|null> $attributes
      */
     public function count(
         string $name,
@@ -51,8 +51,8 @@ public function count(
     }
 
     /**
-     * @param int|float                            $value
-     * @param array<string, int|float|string|bool> $attributes
+     * @param int|float                                 $value
+     * @param array<string, int|float|string|bool|null> $attributes
      */
     public function distribution(
         string $name,
@@ -70,8 +70,8 @@ public function distribution(
     }
 
     /**
-     * @param int|float                            $value
-     * @param array<string, int|float|string|bool> $attributes
+     * @param int|float                                 $value
+     * @param array<string, int|float|string|bool|null> $attributes
      */
     public function gauge(
         string $name,
diff --git a/src/Metrics/Types/CounterMetric.php b/src/Metrics/Types/CounterMetric.php
index ff7d636dc..42710c2b2 100644
--- a/src/Metrics/Types/CounterMetric.php
+++ b/src/Metrics/Types/CounterMetric.php
@@ -24,8 +24,8 @@ final class CounterMetric extends Metric
     private $value;
 
     /**
-     * @param int|float                            $value
-     * @param array<string, int|float|string|bool> $attributes
+     * @param int|float                                 $value
+     * @param array<string, int|float|string|bool|null> $attributes
      */
     public function __construct(
         string $name,
diff --git a/src/Metrics/Types/DistributionMetric.php b/src/Metrics/Types/DistributionMetric.php
index 6d2ea7306..631062001 100644
--- a/src/Metrics/Types/DistributionMetric.php
+++ b/src/Metrics/Types/DistributionMetric.php
@@ -24,8 +24,8 @@ final class DistributionMetric extends Metric
     private $value;
 
     /**
-     * @param int|float                            $value
-     * @param array<string, int|float|string|bool> $attributes
+     * @param int|float                                 $value
+     * @param array<string, int|float|string|bool|null> $attributes
      */
     public function __construct(
         string $name,
diff --git a/src/Metrics/Types/GaugeMetric.php b/src/Metrics/Types/GaugeMetric.php
index 22dc944c2..ae5909fc7 100644
--- a/src/Metrics/Types/GaugeMetric.php
+++ b/src/Metrics/Types/GaugeMetric.php
@@ -24,8 +24,8 @@ final class GaugeMetric extends Metric
     private $value;
 
     /**
-     * @param int|float                            $value
-     * @param array<string, int|float|string|bool> $attributes
+     * @param int|float                                 $value
+     * @param array<string, int|float|string|bool|null> $attributes
      */
     public function __construct(
         string $name,
diff --git a/src/Metrics/Types/Metric.php b/src/Metrics/Types/Metric.php
index a66cbd6ea..d74cf424a 100644
--- a/src/Metrics/Types/Metric.php
+++ b/src/Metrics/Types/Metric.php
@@ -42,7 +42,7 @@ abstract class Metric
     private $unit;
 
     /**
-     * @param array<string, int|float|string|bool> $attributes
+     * @param array<string, int|float|string|bool|null> $attributes
      */
     public function __construct(
         string $name,
diff --git a/tests/Metrics/TraceMetricsTest.php b/tests/Metrics/TraceMetricsTest.php
index 1191e076e..7ce43404a 100644
--- a/tests/Metrics/TraceMetricsTest.php
+++ b/tests/Metrics/TraceMetricsTest.php
@@ -192,6 +192,20 @@ public function testFloatType(): void
         $this->assertEquals(10.50, $metric->getValue());
     }
 
+    public function testNullAttributeValueIsStringified(): void
+    {
+        traceMetrics()->count('test-count', 2, ['foo' => null]);
+        traceMetrics()->flush();
+
+        $this->assertCount(1, StubTransport::$events);
+        $event = StubTransport::$events[0];
+
+        $this->assertCount(1, $event->getMetrics());
+        $metric = $event->getMetrics()[0];
+
+        $this->assertSame('null', $metric->getAttributes()->toSimpleArray()['foo']);
+    }
+
     public function testInvalidTypeIsDiscarded(): void
     {
         // @phpstan-ignore-next-line