diff --git a/src/Components/NestedAccessor.php b/src/Components/NestedAccessor.php
index d15b54d..a1687f3 100644
--- a/src/Components/NestedAccessor.php
+++ b/src/Components/NestedAccessor.php
@@ -89,7 +89,12 @@ public function set($path, $value): self
         $source = &$this->getRef($this->getPathStack($path));
 
         if ($source instanceof ProxyInterface) {
-            $source->setValue($value);
+            try {
+                $source->setValue($value);
+            } catch (\BadMethodCallException $e) {
+                [$key, $path] = $this->cutPathTail($path);
+                throw new PathNotWritableException($key, $path, $this->pathDelimiter);
+            }
         } else {
             $source = $value;
         }
diff --git a/tests/unit/NestedAccessor/NestedAccessorSetTest.php b/tests/unit/NestedAccessor/NestedAccessorSetTest.php
index ba4fa95..f30dd1e 100644
--- a/tests/unit/NestedAccessor/NestedAccessorSetTest.php
+++ b/tests/unit/NestedAccessor/NestedAccessorSetTest.php
@@ -5,6 +5,7 @@
 namespace Smoren\Schemator\Tests\Unit\NestedAccessor;
 
 use Smoren\Schemator\Components\NestedAccessor;
+use Smoren\Schemator\Exceptions\PathNotWritableException;
 use Smoren\Schemator\Tests\Unit\Fixtures\ClassWithAccessibleProperties;
 
 class NestedAccessorSetTest extends \Codeception\Test\Unit
@@ -90,6 +91,12 @@ public function dataProviderForArray(): array
                 [1],
                 ['a' => ['b' => ['c' => [0], 'd' => [1]]]],
             ],
+            [
+                ['a' => ['b' => 1]],
+                ['a', 'b', 'd'],
+                [1],
+                ['a' => ['b' => ['d' => [1]]]],
+            ],
         ];
     }
 
@@ -260,4 +267,40 @@ public function dataProviderForObject(): array
             ],
         ];
     }
+
+    /**
+     * @dataProvider dataProviderForPathNotWritable
+     */
+    public function testPathNotWritable($source, $path, $value)
+    {
+        // Given
+        $accessor = new NestedAccessor($source);
+
+        // Then
+        $this->expectException(PathNotWritableException::class);
+
+        // When
+        $accessor->set($path, $value);
+    }
+
+    public function dataProviderForPathNotWritable(): array
+    {
+        return [
+            [
+                new ClassWithAccessibleProperties(),
+                'protectedProperty',
+                22,
+            ],
+            [
+                new ClassWithAccessibleProperties(),
+                'privateProperty',
+                22,
+            ],
+            [
+                1,
+                'test',
+                22,
+            ],
+        ];
+    }
 }