diff --git a/cache.h b/cache.h
index f4bb43ec6a..16a8c7c23c 100644
--- a/cache.h
+++ b/cache.h
@@ -784,6 +784,9 @@ extern int force_object_loose(const unsigned char *sha1, time_t mtime);
 /* global flag to enable extra checks when accessing packed objects */
 extern int do_check_packed_object_crc;
 
+/* for development: log offset of pack access */
+extern const char *log_pack_access;
+
 extern int check_sha1_signature(const unsigned char *sha1, void *buf, unsigned long size, const char *type);
 
 extern int move_temp_to_file(const char *tmpfile, const char *filename);
diff --git a/config.c b/config.c
index e0b3b80d92..5ef3f397d5 100644
--- a/config.c
+++ b/config.c
@@ -569,6 +569,9 @@ static int git_default_core_config(const char *var, const char *value)
 		return 0;
 	}
 
+	if (!strcmp(var, "core.logpackaccess"))
+		return git_config_string(&log_pack_access, var, value);
+
 	if (!strcmp(var, "core.autocrlf")) {
 		if (value && !strcasecmp(value, "input")) {
 			if (core_eol == EOL_CRLF)
diff --git a/environment.c b/environment.c
index 94d58fd244..19351024f5 100644
--- a/environment.c
+++ b/environment.c
@@ -36,6 +36,7 @@ size_t packed_git_window_size = DEFAULT_PACKED_GIT_WINDOW_SIZE;
 size_t packed_git_limit = DEFAULT_PACKED_GIT_LIMIT;
 size_t delta_base_cache_limit = 16 * 1024 * 1024;
 unsigned long big_file_threshold = 512 * 1024 * 1024;
+const char *log_pack_access;
 const char *pager_program;
 int pager_use_color = 1;
 const char *editor_program;
diff --git a/sha1_file.c b/sha1_file.c
index 064a330408..baf5da1823 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -1839,6 +1839,24 @@ static void *unpack_delta_entry(struct packed_git *p,
 	return result;
 }
 
+static void write_pack_access_log(struct packed_git *p, off_t obj_offset)
+{
+	static FILE *log_file;
+
+	if (!log_file) {
+		log_file = fopen(log_pack_access, "w");
+		if (!log_file) {
+			error("cannot open pack access log '%s' for writing: %s",
+			      log_pack_access, strerror(errno));
+			log_pack_access = NULL;
+			return;
+		}
+	}
+	fprintf(log_file, "%s %"PRIuMAX"\n",
+		p->pack_name, (uintmax_t)obj_offset);
+	fflush(log_file);
+}
+
 int do_check_packed_object_crc;
 
 void *unpack_entry(struct packed_git *p, off_t obj_offset,
@@ -1848,6 +1866,9 @@ void *unpack_entry(struct packed_git *p, off_t obj_offset,
 	off_t curpos = obj_offset;
 	void *data;
 
+	if (log_pack_access)
+		write_pack_access_log(p, obj_offset);
+
 	if (do_check_packed_object_crc && p->index_version > 1) {
 		struct revindex_entry *revidx = find_pack_revindex(p, obj_offset);
 		unsigned long len = revidx[1].offset - obj_offset;