diff --git a/src/JsonPatch.php b/src/JsonPatch.php
index 62a80f2..ccd4c99 100644
--- a/src/JsonPatch.php
+++ b/src/JsonPatch.php
@@ -60,11 +60,15 @@ public static function import(array $data)
                 $operation = (object)$operation;
             }
 
+            if (!is_object($operation)) {
+                throw new Exception( 'Invalid patch operation - should be a JSON object' );
+            }
+
             if (!isset($operation->op)) {
-                throw new Exception('Missing "op" in operation data');
+                throw new MissingFieldException('op', $operation);
             }
             if (!isset($operation->path)) {
-                throw new Exception('Missing "path" in operation data');
+                throw new MissingFieldException('path', $operation);
             }
 
             $op = null;
@@ -88,18 +92,18 @@ public static function import(array $data)
                     $op = new Test();
                     break;
                 default:
-                    throw new Exception('Unknown "op": ' . $operation->op);
+                    throw new UnknownOperationException($operation);
             }
             $op->path = $operation->path;
             if ($op instanceof OpPathValue) {
                 if (property_exists($operation, 'value')) {
                     $op->value = $operation->value;
                 } else {
-                    throw new Exception('Missing "value" in operation data');
+                    throw new MissingFieldException('value', $operation);
                 }
             } elseif ($op instanceof OpPathFrom) {
                 if (!isset($operation->from)) {
-                    throw new Exception('Missing "from" in operation data');
+                    throw new MissingFieldException('from', $operation);
                 }
                 $op->from = $operation->from;
             }
diff --git a/src/MissingFieldException.php b/src/MissingFieldException.php
new file mode 100644
index 0000000..915f1dc
--- /dev/null
+++ b/src/MissingFieldException.php
@@ -0,0 +1,47 @@
+<?php
+
+namespace Swaggest\JsonDiff;
+
+use Throwable;
+
+class MissingFieldException extends Exception
+{
+    /** @var string */
+    private $missingField;
+    /** @var object */
+    private $operation;
+
+    /**
+     * @param string $missingField
+     * @param object $operation
+     * @param int $code
+     * @param Throwable|null $previous
+     */
+    public function __construct(
+        $missingField,
+        $operation,
+        $code = 0,
+        Throwable $previous = null
+    )
+    {
+        parent::__construct('Missing "' . $missingField . '" in operation data', $code, $previous);
+        $this->missingField = $missingField;
+        $this->operation = $operation;
+    }
+
+    /**
+     * @return string
+     */
+    public function getMissingField()
+    {
+        return $this->missingField;
+    }
+
+    /**
+     * @return object
+     */
+    public function getOperation()
+    {
+        return $this->operation;
+    }
+}
diff --git a/src/UnknownOperationException.php b/src/UnknownOperationException.php
new file mode 100644
index 0000000..0855bb2
--- /dev/null
+++ b/src/UnknownOperationException.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace Swaggest\JsonDiff;
+
+
+use Throwable;
+
+class UnknownOperationException extends Exception
+{
+    /** @var object */
+    private $operation;
+
+    /**
+     * @param object $operation
+     * @param int $code
+     * @param Throwable|null $previous
+     */
+    public function __construct(
+        $operation,
+        $code = 0,
+        Throwable $previous = null
+    )
+    {
+        // @phpstan-ignore-next-line MissingFieldOperation will be thrown if op is not set
+        parent::__construct('Unknown "op": ' . $operation->op, $code, $previous);
+        $this->operation = $operation;
+    }
+
+    /**
+     * @return object
+     */
+    public function getOperation()
+    {
+        return $this->operation;
+    }
+}
diff --git a/tests/src/JsonPatchTest.php b/tests/src/JsonPatchTest.php
index 0870442..ce73ab6 100644
--- a/tests/src/JsonPatchTest.php
+++ b/tests/src/JsonPatchTest.php
@@ -5,7 +5,9 @@
 use Swaggest\JsonDiff\Exception;
 use Swaggest\JsonDiff\JsonDiff;
 use Swaggest\JsonDiff\JsonPatch;
+use Swaggest\JsonDiff\MissingFieldException;
 use Swaggest\JsonDiff\PatchTestOperationFailedException;
+use Swaggest\JsonDiff\UnknownOperationException;
 
 class JsonPatchTest extends \PHPUnit_Framework_TestCase
 {
@@ -75,7 +77,7 @@ public function testNull()
 
     public function testMissingOp()
     {
-        $this->setExpectedException(get_class(new Exception()), 'Missing "op" in operation data');
+        $this->setExpectedException(MissingFieldException::class, 'Missing "op" in operation data');
         JsonPatch::import(array((object)array('path' => '/123')));
     }
 
@@ -87,7 +89,7 @@ public function testMissingPath()
 
     public function testInvalidOp()
     {
-        $this->setExpectedException(get_class(new Exception()), 'Unknown "op": wat');
+        $this->setExpectedException(UnknownOperationException::class, 'Unknown "op": wat');
         JsonPatch::import(array((object)array('op' => 'wat', 'path' => '/123')));
     }