diff --git a/applypatch/applypatch.cpp b/applypatch/applypatch.cpp
index 7104abd..db7530b 100644
--- a/applypatch/applypatch.cpp
+++ b/applypatch/applypatch.cpp
@@ -630,6 +630,11 @@
   SHA_CTX ctx;
   SHA1_Init(&ctx);
   SinkFn sink = [&memory_sink_str, &ctx](const unsigned char* data, size_t len) {
+    if (len != 0) {
+      uint8_t digest[SHA_DIGEST_LENGTH];
+      SHA1(data, len, digest);
+      LOG(DEBUG) << "Appending " << len << " bytes data, sha1: " << short_sha1(digest);
+    }
     SHA1_Update(&ctx, data, len);
     memory_sink_str.append(reinterpret_cast<const char*>(data), len);
     return len;
diff --git a/applypatch/imgpatch.cpp b/applypatch/imgpatch.cpp
index 2e4faaa..9794a48 100644
--- a/applypatch/imgpatch.cpp
+++ b/applypatch/imgpatch.cpp
@@ -182,6 +182,8 @@
         printf("Failed to apply bsdiff patch.\n");
         return -1;
       }
+
+      LOG(DEBUG) << "Processed chunk type normal";
     } else if (type == CHUNK_RAW) {
       const char* raw_header = patch_header + pos;
       pos += 4;
@@ -201,6 +203,8 @@
         return -1;
       }
       pos += data_len;
+
+      LOG(DEBUG) << "Processed chunk type raw";
     } else if (type == CHUNK_DEFLATE) {
       // deflate chunks have an additional 60 bytes in their chunk header.
       const char* deflate_header = patch_header + pos;
@@ -276,6 +280,7 @@
         return -1;
       }
 
+      LOG(DEBUG) << "Processed chunk type deflate";
     } else {
       printf("patch chunk %d is unknown type %d\n", i, type);
       return -1;