diff --git a/I2C_serial_pi2.py b/I2C_serial_pi2.py
index f85dc662cfd8e3b3070ef93376ad0ab23981de9e..5ae5af3976e9d28807f0eaa4b0f894a72ff1b8ec 100644
--- a/I2C_serial_pi2.py
+++ b/I2C_serial_pi2.py
@@ -38,6 +38,8 @@ class I2C:
         try:
             (count, rd_value) = pi.i2c_read_i2c_block_data(bus, register, bytes_to_read)
             ret_value = ''
+            if len(rd_value) < bytes_to_read:
+                return False, 999
             for cnt in range(bytes_to_read):
                 ret_value += (hex(rd_value[cnt])[2:])
             ret_ack = 1