--- libtiff/tif_lzw.c
+++ libtiff/tif_lzw.c
@@ -408,6 +408,8 @@
 			break;
 		if (code == CODE_CLEAR) {
 			free_entp = sp->dec_codetab + CODE_FIRST;
+			_TIFFmemset(free_entp, 0, (CSIZE-CODE_FIRST)*sizeof (code_t));
+			_TIFFmemset(free_entp, 0, (CSIZE-CODE_FIRST)*sizeof (code_t));
 			nbits = BITS_MIN;
 			nbitsmask = MAXCODE(BITS_MIN);
 			maxcodep = sp->dec_codetab + nbitsmask-1;
@@ -604,6 +606,7 @@
 			break;
 		if (code == CODE_CLEAR) {
 			free_entp = sp->dec_codetab + CODE_FIRST;
+			_TIFFmemset(free_entp, 0, (CSIZE-CODE_FIRST)*sizeof (code_t));
 			nbits = BITS_MIN;
 			nbitsmask = MAXCODE(BITS_MIN);
 			maxcodep = sp->dec_codetab + nbitsmask;