+--- a/trees.c
++++ b/trees.c
+@@ -856,9 +856,10 @@
+ * trees or store, and output the encoded block to the zip file. This function
+ * returns the total compressed length for the file so far.
+ */
+-off_t flush_block(buf, stored_len, eof)
++off_t flush_block(buf, stored_len, pad, eof)
+ char *buf; /* input block, or NULL if too old */
+ ulg stored_len; /* length of input block */
++ int pad; /* pad output to byte boundary */
+ int eof; /* true if this is the last block for a file */
+ {
+ ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */
+@@ -951,6 +952,10 @@
+ Assert (input_len == bytes_in, "bad input size");
+ bi_windup();
+ compressed_len += 7; /* align on byte boundary */
++ } else if (pad && (compressed_len % 8) != 0) {
++ send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */
++ compressed_len = (compressed_len + 3 + 7) & ~7L;
++ copy_block(buf, 0, 1); /* with header */
+ }
+
+ return compressed_len >> 3;