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;
diff --git a/tests/component/applypatch_test.cpp b/tests/component/applypatch_test.cpp
index f19f28c..292d76e 100644
--- a/tests/component/applypatch_test.cpp
+++ b/tests/component/applypatch_test.cpp
@@ -31,6 +31,7 @@
 #include <vector>
 
 #include <android-base/file.h>
+#include <android-base/logging.h>
 #include <android-base/stringprintf.h>
 #include <android-base/test_utils.h>
 #include <android-base/unique_fd.h>
@@ -46,7 +47,7 @@
 using namespace std::string_literals;
 
 static void sha1sum(const std::string& fname, std::string* sha1, size_t* fsize = nullptr) {
-  ASSERT_NE(nullptr, sha1);
+  ASSERT_TRUE(sha1 != nullptr);
 
   std::string data;
   ASSERT_TRUE(android::base::ReadFileToString(fname, &data));
@@ -68,6 +69,14 @@
   ASSERT_TRUE(android::base::WriteStringToFile(content, fname));
 }
 
+static void test_logger(android::base::LogId /* id */, android::base::LogSeverity severity,
+                        const char* /* tag */, const char* /* file */, unsigned int /* line */,
+                        const char* message) {
+  if (severity >= android::base::GetMinimumLogSeverity()) {
+    fprintf(stdout, "%s\n", message);
+  }
+}
+
 class ApplyPatchTest : public ::testing::Test {
  public:
   virtual void SetUp() override {
@@ -109,6 +118,8 @@
  protected:
   void SetUp() override {
     CacheLocation::location().set_cache_temp_source(cache_source.path);
+    android::base::InitLogging(nullptr, &test_logger);
+    android::base::SetMinimumLogSeverity(android::base::LogSeverity::DEBUG);
   }
 
   TemporaryFile cache_source;