diff --git a/usbtmc/usbtmc.py b/usbtmc/usbtmc.py
index 5e38af0..1773d29 100644
--- a/usbtmc/usbtmc.py
+++ b/usbtmc/usbtmc.py
@@ -655,6 +655,9 @@ def read_raw(self, num=-1):
 
                 resp = self.bulk_in_ep.read(read_len+USBTMC_HEADER_SIZE+3, timeout=self._timeout_ms)
 
+                if len(resp) < 4:
+                    raise usb.core.USBError('Operation timed out', errno=110)
+
                 if sys.version_info >= (3, 2):
                     resp = resp.tobytes()
                 else: