diff --git a/wagtail/wagtailimages/checks.py b/wagtail/wagtailimages/checks.py
index 9c2235eb5..bf785682d 100644
--- a/wagtail/wagtailimages/checks.py
+++ b/wagtail/wagtailimages/checks.py
@@ -1,52 +1,37 @@
 import os
 
 from django.core.checks import register, Warning
+from django.utils.lru_cache import lru_cache
 
 from willow.image import Image
 
 
-_has_jpeg_support = None
-_has_png_support = None
-
-
+@lru_cache()
 def has_jpeg_support():
-    global _has_jpeg_support
-
-    if _has_jpeg_support is None:
-        wagtail_jpg = os.path.join(os.path.dirname(__file__), 'check_files', 'wagtail.jpg')
-        succeeded = True
-        f = open(wagtail_jpg, 'rb')
+    wagtail_jpg = os.path.join(os.path.dirname(__file__), 'check_files', 'wagtail.jpg')
+    succeeded = True
 
+    with open(wagtail_jpg, 'rb') as f:
         try:
             Image.open(f)
         except (IOError, Image.LoaderError):
             succeeded = False
-        finally:
-            f.close()
 
-        _has_jpeg_support = succeeded
-
-    return _has_jpeg_support
+    return succeeded
 
 
+@lru_cache()
 def has_png_support():
-    global _has_png_support
-
-    if _has_png_support is None:
-        wagtail_png = os.path.join(os.path.dirname(__file__), 'check_files', 'wagtail.png')
-        succeeded = True
-        f = open(wagtail_png, 'rb')
+    wagtail_png = os.path.join(os.path.dirname(__file__), 'check_files', 'wagtail.png')
+    succeeded = True
 
+    with open(wagtail_png, 'rb') as f:
         try:
             Image.open(f)
         except (IOError, Image.LoaderError):
             succeeded = False
-        finally:
-            f.close()
 
-        _has_png_support = succeeded
-
-    return _has_png_support
+    return succeeded
 
 
 @register()