diff --git a/emcc.c b/emcc.c
index 5f21476..9f46c33 100644
--- a/emcc.c
+++ b/emcc.c
@@ -773,53 +773,12 @@ struct savefile_write_ctx {
     size_t pos;
 };
 
-static void savefile_write(void *vctx, const void *vbuf, int len)
+static void savefile_write(void *vctx, const void *buf, int len)
 {
-    static const unsigned char length[256] = {
-        /*
-         * Assign a length of 1 to any printable ASCII character that
-         * can be written literally in URI-encoding, i.e.
-         *
-         *    A-Z a-z 0-9 - _ . ! ~ * ' ( )
-         *
-         * Assign length 3 (for % and two hex digits) to all other
-         * byte values.
-         */
-        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
-        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
-        3, 1, 3, 3, 3, 3, 3, 1, 1, 1, 1, 3, 3, 1, 1, 3,
-        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 3, 3, 3, 3,
-        3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 3, 3, 1,
-        3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 3, 1, 3,
-        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
-        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
-        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
-        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
-        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
-        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
-        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
-        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
-    };
-    static const char hexdigits[] = "0123456789ABCDEF";
-
     struct savefile_write_ctx *ctx = (struct savefile_write_ctx *)vctx;
-    const unsigned char *buf = (const unsigned char *)vbuf;
-    for (int i = 0; i < len; i++) {
-        unsigned char c = buf[i];
-        int clen = length[c];
-        if (ctx->buffer) {
-            if (clen == 1) {
-                ctx->buffer[ctx->pos] = c;
-            } else {
-                ctx->buffer[ctx->pos] = '%';
-                ctx->buffer[ctx->pos+1] = hexdigits[c >> 4];
-                ctx->buffer[ctx->pos+2] = hexdigits[c & 0xF];
-            }
-        }
-        ctx->pos += clen;
-    }
+    if (ctx->buffer)
+        memcpy(ctx->buffer + ctx->pos, buf, len);
+    ctx->pos += len;
 }
 
 char *get_save_file(void)
diff --git a/emccpre.js b/emccpre.js
index b4ab82d..aa2803e 100644
--- a/emccpre.js
+++ b/emccpre.js
@@ -363,7 +363,8 @@ function initPuzzle() {
                 "Click to download the "));
             var a = document.createElement("a");
             a.download = "puzzle.sav";
-            a.href = "data:application/octet-stream," + savefile_text;
+            a.href = "data:application/octet-stream," +
+                encodeURIComponent(savefile_text);
             a.appendChild(document.createTextNode("saved-game file"));
             dlg_form.appendChild(a);
             dlg_form.appendChild(document.createTextNode("."));