diff --git a/mozilla/nsprpub/lib/libc/src/base64.c b/mozilla/nsprpub/lib/libc/src/base64.c
index 749965f7552..00f19ab2053 100644
--- a/mozilla/nsprpub/lib/libc/src/base64.c
+++ b/mozilla/nsprpub/lib/libc/src/base64.c
@@ -383,7 +383,7 @@ PL_Base64Decode
         srclen = PL_strlen(src);
     }
 
-    if( 0 == (srclen & 3) )
+    if( srclen && (0 == (srclen & 3)) )
     {
         if( (char)'=' == src[ srclen-1 ] )
         {