diff --git a/yt/utilities/png_writer.py b/yt/utilities/png_writer.py
index 475e113ee56..e4b5cef74f6 100644
--- a/yt/utilities/png_writer.py
+++ b/yt/utilities/png_writer.py
@@ -18,13 +18,14 @@
 else:
     from io import BytesIO as StringIO
 
-def call_png_write_png(buffer, width, height, filename, dpi):
+def call_png_write_png(buffer, width, height, fileobj, dpi):
     _png.write_png(buffer, filename, dpi)
 
 def write_png(buffer, filename, dpi=100):
     width = buffer.shape[1]
     height = buffer.shape[0]
-    call_png_write_png(buffer, width, height, filename, dpi)
+    with open(filename, "wb") as fileobj:
+        call_png_write_png(buffer, width, height, fileobj, dpi)
 
 def write_png_to_string(buffer, dpi=100, gray=0):
     width = buffer.shape[1]