diff --git a/psalm-baseline.xml b/psalm-baseline.xml
index 97bdba8f9..d61391fef 100644
--- a/psalm-baseline.xml
+++ b/psalm-baseline.xml
@@ -288,8 +288,7 @@
     </MixedReturnStatement>
   </file>
   <file src="src/Model/SearchIndexInput.php">
-    <DocblockTypeContradiction occurrences="2">
-      <code>! is_array($index['definition']) &amp;&amp; ! is_object($index['definition'])</code>
+    <DocblockTypeContradiction occurrences="1">
       <code>isset($index['name']) &amp;&amp; ! is_string($index['name'])</code>
     </DocblockTypeContradiction>
   </file>
@@ -444,11 +443,8 @@
     </MixedMethodCall>
   </file>
   <file src="src/Operation/CreateSearchIndexes.php">
-    <DocblockTypeContradiction occurrences="1">
-      <code>is_array($index)</code>
-    </DocblockTypeContradiction>
     <MixedArgumentTypeCoercion occurrences="1">
-      <code>$index</code>
+      <code>(array) $index</code>
     </MixedArgumentTypeCoercion>
   </file>
   <file src="src/Operation/DatabaseCommand.php">
@@ -715,11 +711,6 @@
       <code>! is_array($update) &amp;&amp; ! is_object($update)</code>
     </DocblockTypeContradiction>
   </file>
-  <file src="src/Operation/UpdateSearchIndex.php">
-    <DocblockTypeContradiction occurrences="1">
-      <code>! is_array($definition) &amp;&amp; ! is_object($definition)</code>
-    </DocblockTypeContradiction>
-  </file>
   <file src="src/Operation/Watch.php">
     <DocblockTypeContradiction occurrences="1">
       <code>isset($resumeToken) &amp;&amp; ! is_array($resumeToken) &amp;&amp; ! is_object($resumeToken)</code>
@@ -785,18 +776,13 @@
       <code>$typeMap['fieldPaths'][$fieldPath]</code>
       <code>$value</code>
     </MixedAssignment>
-    <MixedInferredReturnType occurrences="3">
-      <code>array|object</code>
+    <MixedInferredReturnType occurrences="2">
       <code>array|object|null</code>
       <code>array|object|null</code>
     </MixedInferredReturnType>
-    <MixedOperand occurrences="1">
-      <code>$type</code>
-    </MixedOperand>
-    <MixedReturnStatement occurrences="3">
+    <MixedReturnStatement occurrences="2">
       <code>$collectionInfo['options']['encryptedFields'] ?? null</code>
       <code>$encryptedFieldsMap[$databaseName . '.' . $collectionName] ?? null</code>
-      <code>toPHP(fromPHP($document), $typeMap)</code>
     </MixedReturnStatement>
   </file>
 </files>
diff --git a/src/Model/SearchIndexInput.php b/src/Model/SearchIndexInput.php
index 616e15f93..a75e0d63c 100644
--- a/src/Model/SearchIndexInput.php
+++ b/src/Model/SearchIndexInput.php
@@ -20,9 +20,8 @@
 use MongoDB\BSON\Serializable;
 use MongoDB\Exception\InvalidArgumentException;
 
-use function is_array;
-use function is_object;
 use function is_string;
+use function MongoDB\is_document;
 
 /**
  * Search index input model class.
@@ -49,8 +48,8 @@ public function __construct(array $index)
             throw new InvalidArgumentException('Required "definition" document is missing from search index specification');
         }
 
-        if (! is_array($index['definition']) && ! is_object($index['definition'])) {
-            throw InvalidArgumentException::invalidType('"definition" option', $index['definition'], 'array or object');
+        if (! is_document($index['definition'])) {
+            throw InvalidArgumentException::expectedDocumentType('"definition" option', $index['definition']);
         }
 
         // Name is optional, but must be a non-empty string if provided
diff --git a/src/Operation/CreateSearchIndexes.php b/src/Operation/CreateSearchIndexes.php
index 04325b82c..77980991f 100644
--- a/src/Operation/CreateSearchIndexes.php
+++ b/src/Operation/CreateSearchIndexes.php
@@ -27,8 +27,7 @@
 use function array_is_list;
 use function array_map;
 use function current;
-use function is_array;
-use function is_object;
+use function MongoDB\is_document;
 use function sprintf;
 
 /**
@@ -64,13 +63,11 @@ public function __construct(string $databaseName, string $collectionName, array
         }
 
         foreach ($indexes as $i => $index) {
-            if (is_object($index)) {
-                $index = (array) $index;
-            } elseif (! is_array($index)) {
-                throw InvalidArgumentException::invalidType(sprintf('$index[%d]', $i), $index, 'array or object');
+            if (! is_document($index)) {
+                throw InvalidArgumentException::expectedDocumentType(sprintf('$indexes[%d]', $i), $index);
             }
 
-            $this->indexes[] = new SearchIndexInput($index);
+            $this->indexes[] = new SearchIndexInput((array) $index);
         }
 
         $this->databaseName = $databaseName;
diff --git a/src/Operation/UpdateSearchIndex.php b/src/Operation/UpdateSearchIndex.php
index 84eb5e383..5a85a69a7 100644
--- a/src/Operation/UpdateSearchIndex.php
+++ b/src/Operation/UpdateSearchIndex.php
@@ -23,8 +23,7 @@
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
 
-use function is_array;
-use function is_object;
+use function MongoDB\is_document;
 
 /**
  * Operation for the createIndexes command.
@@ -61,8 +60,8 @@ public function __construct(string $databaseName, string $collectionName, string
             throw new InvalidArgumentException('Index name cannot be empty');
         }
 
-        if (! is_array($definition) && ! is_object($definition)) {
-            throw InvalidArgumentException::invalidType('$definition', $definition, 'array or object');
+        if (! is_document($definition)) {
+            throw InvalidArgumentException::expectedDocumentType('$definition', $definition);
         }
 
         $this->databaseName = $databaseName;
diff --git a/tests/Model/IndexInputTest.php b/tests/Model/IndexInputTest.php
index 7708055cc..e9dad4f89 100644
--- a/tests/Model/IndexInputTest.php
+++ b/tests/Model/IndexInputTest.php
@@ -15,12 +15,14 @@ class IndexInputTest extends TestCase
     public function testConstructorShouldRequireKey(): void
     {
         $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Required "key" document is missing from index specification');
         new IndexInput([]);
     }
 
     public function testConstructorShouldRequireKeyToBeArrayOrObject(): void
     {
         $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected "key" option to have type "document"');
         new IndexInput(['key' => 'foo']);
     }
 
@@ -28,6 +30,7 @@ public function testConstructorShouldRequireKeyToBeArrayOrObject(): void
     public function testConstructorShouldRequireKeyFieldOrderToBeNumericOrString($order): void
     {
         $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected order value for "x" field within "key" option to have type "numeric or string"');
         new IndexInput(['key' => ['x' => $order]]);
     }
 
@@ -39,6 +42,7 @@ public function provideInvalidFieldOrderValues()
     public function testConstructorShouldRequireNameToBeString(): void
     {
         $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected "name" option to have type "string"');
         new IndexInput(['key' => ['x' => 1], 'name' => 1]);
     }
 
diff --git a/tests/Model/SearchIndexInputTest.php b/tests/Model/SearchIndexInputTest.php
new file mode 100644
index 000000000..3c6fbe142
--- /dev/null
+++ b/tests/Model/SearchIndexInputTest.php
@@ -0,0 +1,48 @@
+<?php
+
+namespace MongoDB\Tests\Model;
+
+use MongoDB\BSON\Serializable;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Model\SearchIndexInput;
+use MongoDB\Tests\TestCase;
+
+class SearchIndexInputTest extends TestCase
+{
+    public function testConstructorIndexDefinitionMustBeDefined(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Required "definition" document is missing from search index specification');
+        new SearchIndexInput([]);
+    }
+
+    public function testConstructorIndexDefinitionMustBeADocument(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected "definition" option to have type "document"');
+        new SearchIndexInput(['definition' => 'foo']);
+    }
+
+    public function testConstructorShouldRequireNameToBeString(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected "name" option to have type "string"');
+        new SearchIndexInput(['definition' => ['mapping' => ['dynamid' => true]], 'name' => 1]);
+    }
+
+    public function testBsonSerialization(): void
+    {
+        $expected = (object) [
+            'name' => 'my_search',
+            'definition' => ['mapping' => ['dynamic' => true]],
+        ];
+
+        $indexInput = new SearchIndexInput([
+            'name' => 'my_search',
+            'definition' => ['mapping' => ['dynamic' => true]],
+        ]);
+
+        $this->assertInstanceOf(Serializable::class, $indexInput);
+        $this->assertEquals($expected, $indexInput->bsonSerialize());
+    }
+}
diff --git a/tests/Operation/CreateSearchIndexesTest.php b/tests/Operation/CreateSearchIndexesTest.php
index d8e3b240f..03e6e31ee 100644
--- a/tests/Operation/CreateSearchIndexesTest.php
+++ b/tests/Operation/CreateSearchIndexesTest.php
@@ -18,7 +18,7 @@ public function testConstructorIndexesArgumentMustBeAList(): void
     public function testConstructorIndexDefinitionMustBeADocument($index): void
     {
         $this->expectException(InvalidArgumentException::class);
-        $this->expectExceptionMessage('Expected $index[0] to have type "array or object"');
+        $this->expectExceptionMessage('Expected $indexes[0] to have type "document"');
         new CreateSearchIndexes($this->getDatabaseName(), $this->getCollectionName(), [$index]);
     }
 
@@ -41,7 +41,7 @@ public function testConstructorIndexDefinitionMustBeDefined(): void
     public function testConstructorIndexDefinitionMustBeAnArray($definition): void
     {
         $this->expectException(InvalidArgumentException::class);
-        $this->expectExceptionMessage('Expected "definition" option to have type "array or object"');
+        $this->expectExceptionMessage('Expected "definition" option to have type "document"');
         new CreateSearchIndexes($this->getDatabaseName(), $this->getCollectionName(), [['definition' => $definition]]);
     }
 
diff --git a/tests/Operation/UpdateSearchIndexTest.php b/tests/Operation/UpdateSearchIndexTest.php
index 535f620cc..90c623fc3 100644
--- a/tests/Operation/UpdateSearchIndexTest.php
+++ b/tests/Operation/UpdateSearchIndexTest.php
@@ -17,7 +17,7 @@ public function testConstructorIndexNameMustNotBeEmpty(): void
     public function testConstructorIndexDefinitionMustBeADocument($definition): void
     {
         $this->expectException(InvalidArgumentException::class);
-        $this->expectExceptionMessage('Expected $definition to have type "array or object"');
+        $this->expectExceptionMessage('Expected $definition to have type "document"');
         new UpdateSearchIndex($this->getDatabaseName(), $this->getCollectionName(), 'index name', $definition);
     }
 }