diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 10682f58dc..8100bee67e 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -401,7 +401,7 @@ int64_t qmp_guest_file_open(const char *path, bool has_mode, const char *mode, E
         return -1;
     }
 
-    slog("guest-file-open, handle: %d", handle);
+    slog("guest-file-open, handle: %" PRId64, handle);
     return handle;
 }
 
@@ -410,7 +410,7 @@ void qmp_guest_file_close(int64_t handle, Error **err)
     GuestFileHandle *gfh = guest_file_handle_find(handle, err);
     int ret;
 
-    slog("guest-file-close called, handle: %ld", handle);
+    slog("guest-file-close called, handle: %" PRId64, handle);
     if (!gfh) {
         return;
     }
@@ -451,7 +451,7 @@ struct GuestFileRead *qmp_guest_file_read(int64_t handle, bool has_count,
     read_count = fread(buf, 1, count, fh);
     if (ferror(fh)) {
         error_setg_errno(err, errno, "failed to read file");
-        slog("guest-file-read failed, handle: %ld", handle);
+        slog("guest-file-read failed, handle: %" PRId64, handle);
     } else {
         buf[read_count] = 0;
         read_data = g_malloc0(sizeof(GuestFileRead));
@@ -496,7 +496,7 @@ GuestFileWrite *qmp_guest_file_write(int64_t handle, const char *buf_b64,
     write_count = fwrite(buf, 1, count, fh);
     if (ferror(fh)) {
         error_setg_errno(err, errno, "failed to write to file");
-        slog("guest-file-write failed, handle: %ld", handle);
+        slog("guest-file-write failed, handle: %" PRId64, handle);
     } else {
         write_data = g_malloc0(sizeof(GuestFileWrite));
         write_data->count = write_count;
diff --git a/qga/guest-agent-core.h b/qga/guest-agent-core.h
index 624a559d94..e422208b4e 100644
--- a/qga/guest-agent-core.h
+++ b/qga/guest-agent-core.h
@@ -29,7 +29,7 @@ GACommandState *ga_command_state_new(void);
 bool ga_logging_enabled(GAState *s);
 void ga_disable_logging(GAState *s);
 void ga_enable_logging(GAState *s);
-void slog(const gchar *fmt, ...);
+void GCC_FMT_ATTR(1, 2) slog(const gchar *fmt, ...);
 void ga_set_response_delimited(GAState *s);
 bool ga_is_frozen(GAState *s);
 void ga_set_frozen(GAState *s);