diff --git a/src/AbstractSerializer.php b/src/AbstractSerializer.php
index b18ee6b4..ee4b3f88 100644
--- a/src/AbstractSerializer.php
+++ b/src/AbstractSerializer.php
@@ -95,7 +95,7 @@ protected static function splitStream(StreamInterface $stream) : array
                 if (! isset($headers[$currentHeader])) {
                     $headers[$currentHeader] = [];
                 }
-                $headers[$currentHeader][] = ltrim($matches['value']);
+                $headers[$currentHeader][] = trim($matches['value'], "\t ");
                 continue;
             }
 
@@ -109,7 +109,7 @@ protected static function splitStream(StreamInterface $stream) : array
 
             // Append continuation to last header value found
             $value = array_pop($headers[$currentHeader]);
-            $headers[$currentHeader][] = $value . ' ' . ltrim($line);
+            $headers[$currentHeader][] = $value . ' ' . trim($line, "\t ");
         }
 
         // use RelativeStream to avoid copying initial stream into memory
diff --git a/src/MessageTrait.php b/src/MessageTrait.php
index f4fa0ec5..d12e2088 100644
--- a/src/MessageTrait.php
+++ b/src/MessageTrait.php
@@ -398,7 +398,8 @@ private function filterHeaderValue($values) : array
         return array_map(function ($value) {
             HeaderSecurity::assertValid($value);
 
-            return (string) $value;
+            // Remove optional whitespace (OWS, RFC 7230#3.2.3) around the header value.
+            return trim((string) $value, "\t ");
         }, array_values($values));
     }
 
diff --git a/test/MessageTraitTest.php b/test/MessageTraitTest.php
index bbb39cef..e493f65d 100644
--- a/test/MessageTraitTest.php
+++ b/test/MessageTraitTest.php
@@ -336,6 +336,27 @@ public function testWithAddedHeaderAllowsHeaderContinuations(): void
         $this->assertSame("value,\r\n second value", $message->getHeaderLine('X-Foo-Bar'));
     }
 
+    /** @return non-empty-array<non-empty-string, array{non-empty-string}> */
+    public function headersWithWhitespace(): array
+    {
+        return [
+            'no' => ["Baz"],
+            'leading' => [" Baz"],
+            'trailing' => ["Baz "],
+            'both' => [" Baz "],
+            'mixed' => [" \t Baz\t \t"],
+        ];
+    }
+
+    /**
+     * @dataProvider headersWithWhitespace
+     */
+    public function testWithHeaderTrimsWhitespace(string $value): void
+    {
+        $message = $this->message->withHeader('X-Foo-Bar', $value);
+        $this->assertSame(trim($value, "\t "), $message->getHeaderLine('X-Foo-Bar'));
+    }
+
     /** @return non-empty-array<non-empty-string, array{int|float}> */
     public function numericHeaderValuesProvider(): array
     {
diff --git a/test/Request/SerializerTest.php b/test/Request/SerializerTest.php
index 92af8003..2f9d9c3a 100644
--- a/test/Request/SerializerTest.php
+++ b/test/Request/SerializerTest.php
@@ -247,6 +247,30 @@ public function testCanDeserializeResponseWithHeaderContinuations($text) : void
         $this->assertSame('Baz; Bat', $request->getHeaderLine('X-Foo-Bar'));
     }
 
+    /** @return non-empty-array<non-empty-string, array{non-empty-string}> */
+    public function headersWithWhitespace(): array
+    {
+        return [
+            'no' => ["POST /foo HTTP/1.0\r\nContent-Type: text/plain\r\nX-Foo-Bar:Baz\r\n\r\nContent!"],
+            'leading' => ["POST /foo HTTP/1.0\r\nContent-Type: text/plain\r\nX-Foo-Bar: Baz\r\n\r\nContent!"],
+            'trailing' => ["POST /foo HTTP/1.0\r\nContent-Type: text/plain\r\nX-Foo-Bar:Baz \r\n\r\nContent!"],
+            'both' => ["POST /foo HTTP/1.0\r\nContent-Type: text/plain\r\nX-Foo-Bar: Baz \r\n\r\nContent!"],
+            'mixed' => ["POST /foo HTTP/1.0\r\nContent-Type: text/plain\r\nX-Foo-Bar: \t Baz\t \t\r\n\r\nContent!"],
+        ];
+    }
+
+    /**
+     * @dataProvider headersWithWhitespace
+     */
+    public function testDeserializationRemovesWhitespaceAroundValues(string $text): void
+    {
+        $request = Serializer::fromString($text);
+
+        $this->assertInstanceOf(Request::class, $request);
+
+        $this->assertSame('Baz', $request->getHeaderLine('X-Foo-Bar'));
+    }
+
     public function messagesWithInvalidHeaders() : array
     {
         return [
diff --git a/test/Response/SerializerTest.php b/test/Response/SerializerTest.php
index 0f3d456f..fce27a49 100644
--- a/test/Response/SerializerTest.php
+++ b/test/Response/SerializerTest.php
@@ -121,6 +121,30 @@ public function testCanDeserializeResponseWithHeaderContinuations($text)
         $this->assertSame('Baz; Bat', $response->getHeaderLine('X-Foo-Bar'));
     }
 
+    /** @return non-empty-array<non-empty-string, array{non-empty-string}> */
+    public function headersWithWhitespace(): array
+    {
+        return [
+            'no' => ["HTTP/1.0 200 A-OK\r\nContent-Type: text/plain\r\nX-Foo-Bar:Baz\r\n\r\nContent!"],
+            'leading' => ["HTTP/1.0 200 A-OK\r\nContent-Type: text/plain\r\nX-Foo-Bar: Baz\r\n\r\nContent!"],
+            'trailing' => ["HTTP/1.0 200 A-OK\r\nContent-Type: text/plain\r\nX-Foo-Bar:Baz \r\n\r\nContent!"],
+            'both' => ["HTTP/1.0 200 A-OK\r\nContent-Type: text/plain\r\nX-Foo-Bar: Baz \r\n\r\nContent!"],
+            'mixed' => ["HTTP/1.0 200 A-OK\r\nContent-Type: text/plain\r\nX-Foo-Bar: \t Baz\t \t\r\n\r\nContent!"],
+        ];
+    }
+
+    /**
+     * @dataProvider headersWithWhitespace
+     */
+    public function testDeserializationRemovesWhitespaceAroundValues(string $text): void
+    {
+        $response = Serializer::fromString($text);
+
+        $this->assertInstanceOf(Response::class, $response);
+
+        $this->assertSame('Baz', $response->getHeaderLine('X-Foo-Bar'));
+    }
+
     public function testCanDeserializeResponseWithoutBody()
     {
         $text = "HTTP/1.0 204\r\nX-Foo-Bar: Baz";