diff --git a/lisp/gnus/gnus-fun.el b/lisp/gnus/gnus-fun.el
index c95449762e..f1773db29a 100644
--- a/lisp/gnus/gnus-fun.el
+++ b/lisp/gnus/gnus-fun.el
@@ -205,11 +205,27 @@ gnus-face-encode
 (defun gnus-convert-face-to-png (face)
   "Convert FACE (which is base64-encoded) to a PNG.
 The PNG is returned as a string."
-  (mm-with-unibyte-buffer
-    (insert face)
-    (ignore-errors
-      (base64-decode-region (point-min) (point-max)))
-    (buffer-string)))
+  (let ((face (replace-regexp-in-string "[^[:graph:]]" "" face)))
+    ;; Calculate correct base64 padding
+    (if (string-match "=" face)
+	(let ((length (match-beginning 0))
+	      (padding nil))
+	  (progn (setq padding
+		       (/
+			(- 24
+			   (pcase (mod (* length 6) 24)
+			     (`0 24)
+			     (n n)))
+			6))
+		 (setq face (concat
+			     (substring face 0
+					(match-beginning 0))
+			     (make-string padding ?=))))))
+    (mm-with-unibyte-buffer
+      (insert face)
+      (ignore-errors
+	(base64-decode-region (point-min) (point-max)))
+      (buffer-string))))
 
 ;;;###autoload
 (defun gnus-convert-png-to-face (file)