diff --git a/safe_s3_storage/file_validator.py b/safe_s3_storage/file_validator.py
index aa834ac..4f16c26 100644
--- a/safe_s3_storage/file_validator.py
+++ b/safe_s3_storage/file_validator.py
@@ -75,6 +75,13 @@ def _should_convert_file(self, file_name: str) -> bool:
     def _convert_image(self, validated_file: ValidatedFile) -> ValidatedFile:
         import pyvips  # type: ignore[import-untyped] # noqa: PLC0415
 
+        # libvips keeps a process-global operation cache. For one-shot conversions of
+        # unique upload buffers it never hits and only retains memory, so disable it.
+        # The guard makes the setter effectively run once (max is 0 after the first
+        # call) and avoids a module-level global that ruff's ALL ruleset would flag.
+        if pyvips.cache_get_max():
+            pyvips.cache_set_max(0)
+
         if not _is_image(validated_file.mime_type):
             return validated_file
 
diff --git a/tests/test_file_validator.py b/tests/test_file_validator.py
index 4505ce4..efab9a0 100644
--- a/tests/test_file_validator.py
+++ b/tests/test_file_validator.py
@@ -4,6 +4,7 @@
 import faker
 import httpx
 import pytest
+import pyvips  # type: ignore[import-untyped]
 from httpx import codes as status_codes
 
 from safe_s3_storage import exceptions
@@ -212,3 +213,15 @@ async def test_excluded_conversion_formats(
         assert validated_file.file_name == f"{file_base_name}.{file_extension}"
         assert validated_file.file_content == png_file
         assert validated_file.file_size == len(validated_file.file_content)
+
+    async def test_conversion_does_not_leave_pyvips_operations_cached(
+        self, faker: faker.Faker, png_file: bytes
+    ) -> None:
+        # libvips keeps a process-global operation cache; for one-shot conversions of
+        # unique buffers it only retains memory. The validator must disable it so the
+        # cache does not accumulate across conversions (memory leak).
+        await FileValidator(allowed_mime_types=["image/png"]).validate_file(
+            file_name=f"{faker.pystr()}.png", file_content=png_file
+        )
+
+        assert pyvips.cache_get_size() == 0