diff --git a/src/delta.c b/src/delta.c
index 6ab6aa6b..3acb3e12 100644
--- a/src/delta.c
+++ b/src/delta.c
@@ -50,10 +50,6 @@ struct BLOCK_HDR_PACKED block_hdr {
 #define ext_flash_check_read ext_flash_read
 #endif
 
-#ifndef WOLFBOOT_SECTOR_SIZE
-#   define WOLFBOOT_SECTOR_SIZE 0x1000
-#endif
-
 int wb_patch_init(WB_PATCH_CTX *bm, uint8_t *src, uint32_t ssz, uint8_t *patch,
         uint32_t psz)
 {
@@ -223,20 +219,31 @@ int wb_diff(WB_DIFF_CTX *ctx, uint8_t *patch, uint32_t len)
                 break;
             if ((memcmp(pa, (ctx->src_b + ctx->off_b), BLOCK_HDR_SIZE) == 0)) {
                 uint32_t b_start;
+                /* Identical areas of BLOCK_HDR_SIZE bytes match between the images.
+                 * initialize match_len; blk_start is the relative offset within
+                 * the src image.
+                 */
                 match_len = BLOCK_HDR_SIZE;
                 blk_start = pa - ctx->src_a;
                 b_start = ctx->off_b;
                 pa+= BLOCK_HDR_SIZE;
                 ctx->off_b += BLOCK_HDR_SIZE;
                 while (*pa == *(ctx->src_b + ctx->off_b)) {
-                    match_len++;
-                    pa++;
-                    ctx->off_b++;
-                    if ((uint32_t)(pa - ctx->src_a) >= ctx->size_a)
-                        break;
-                    if ((b_start / WOLFBOOT_SECTOR_SIZE) < (ctx->off_b / WOLFBOOT_SECTOR_SIZE)) {
+                    /* Extend matching block if possible, as long as the
+                     * identical sequence continues.
+                     */
+                    if ((uint32_t)(pa + 1 - ctx->src_a) >= ctx->size_a) {
+                        /* Stop matching if the source image size limit is hit. */
                         break;
                     }
+                    if ((b_start / WOLFBOOT_SECTOR_SIZE) < ((ctx->off_b + 1) / WOLFBOOT_SECTOR_SIZE)) {
+                        /* Stop matching when the sector bound is hit. */
+                        break;
+                    }
+                    /* Increase match len, test next byte */
+                    pa++;
+                    ctx->off_b++;
+                    match_len++;
                 }
                 hdr.esc = ESC;
                 hdr.off[0] = ((blk_start >> 16) & 0x000000FF);
@@ -256,23 +263,42 @@ int wb_diff(WB_DIFF_CTX *ctx, uint8_t *patch, uint32_t len)
             uint32_t pb_end = page_start * WOLFBOOT_SECTOR_SIZE;
             pb = ctx->src_b;
             while (((uint32_t)(pb - ctx->src_b) < pb_end) && (p_off < len)) {
+                /* Check image boundary */
                 if ((ctx->size_b - ctx->off_b) < BLOCK_HDR_SIZE)
                     break;
                 if ((uint32_t)(ctx->size_b - (pb - ctx->src_b)) < BLOCK_HDR_SIZE)
                     break;
+
+                /* Don't try matching backwards if the distance between the two
+                 * blocks is smaller than one sector.
+                 */
                 if (WOLFBOOT_SECTOR_SIZE > (pb - ctx->src_b) - (page_start * WOLFBOOT_SECTOR_SIZE))
                     break;
+
                 if ((memcmp(pb, (ctx->src_b + ctx->off_b), BLOCK_HDR_SIZE) == 0)) {
+                    /* A match was found between the current pointer and a
+                     * previously patched area in the resulting image.
+                     * Initialize match_len and set the blk_start to the beginning
+                     * of the matching area in the image.
+                     */
                     match_len = BLOCK_HDR_SIZE;
                     blk_start = pb - ctx->src_b;
                     pb+= BLOCK_HDR_SIZE;
                     ctx->off_b += BLOCK_HDR_SIZE;
                     while (*pb == *(ctx->src_b + ctx->off_b)) {
-                        match_len++;
+                        /* Extend match as long as the areas have the
+                         * same content. Block skipping in this case is
+                         * not a problem since the distance between the patched
+                         * area and the area to patch is always larger than one
+                         * block size.
+                         */
                         pb++;
-                        ctx->off_b++;
-                        if ((uint32_t)(pb - ctx->src_b) >= pb_end)
+                        if ((uint32_t)(pb - ctx->src_b) >= pb_end) {
+                            pb--;
                             break;
+                        }
+                        match_len++;
+                        ctx->off_b++;
                     }
                     hdr.esc = ESC;
                     hdr.off[0] = ((blk_start >> 16) & 0x000000FF);
diff --git a/tools/delta/bmdiff.c b/tools/delta/bmdiff.c
index 59e2e456..ad11d3fd 100644
--- a/tools/delta/bmdiff.c
+++ b/tools/delta/bmdiff.c
@@ -23,7 +23,6 @@
  */
 #define MODE_DIFF 0
 #define MODE_PATCH 1
-#define BUF_SIZE 4096
 #include <unistd.h>
 #include <stdlib.h>
 #include <stdio.h>
@@ -36,7 +35,7 @@
 #include "delta.h"
 
 #define MAX_SRC_SIZE (1 << 24)
-#define PATCH_BLOCK_SIZE 4096
+#define PATCH_BLOCK_SIZE WOLFBOOT_SECTOR_SIZE
 
 int main(int argc, char *argv[])
 {