diff --git a/tools/tiff2ps.c b/tools/tiff2ps.c
index 82a5d84..3563f30 100644
--- a/tools/tiff2ps.c
+++ b/tools/tiff2ps.c
@@ -2964,7 +2964,9 @@ tsize_t Ascii85EncodeBlock( uint8 * ascii85_p, unsigned f_eod, const uint8 * raw
     
             if ( val32 == 0 )                   /* Special case */
             {
-                ascii85_p[ascii85_l] = 'z';
+                if(ascii85_p != NULL) {
+                    ascii85_p[ascii85_l] = 'z';
+                }
                 rc = 1;
             }
     
diff --git a/tools/tiffcrop.c b/tools/tiffcrop.c
index 722b132..470a18d 100644
--- a/tools/tiffcrop.c
+++ b/tools/tiffcrop.c
@@ -958,7 +958,6 @@ static int readContigTilesIntoBuffer (TIFF* in, uint8* buf,
 		     return 1;
 	    }
           }
-        prev_trailing_bits += trailing_bits;
         /* if (prev_trailing_bits > 7) */
 	/*   prev_trailing_bits-= 8; */
 	}
diff --git a/tools/tiffdump.c b/tools/tiffdump.c
index 3de0062..cb69187 100644
--- a/tools/tiffdump.c
+++ b/tools/tiffdump.c
@@ -229,7 +229,7 @@ dump(int fd, uint64 diroff)
 	else
 		Fatal("Not a TIFF file, bad version number %u (%#x)",
 		    hdr.common.tiff_version, hdr.common.tiff_version);
-	for (i = 0; diroff != 0; i++) {
+	for (i = 0; visited_diroff && (diroff != 0); i++) {
 		for(j=0; j<count_visited_dir; j++)
 		{
 		    if( visited_diroff[j] == diroff )