diff --git a/src/mms/iso_cotp/cotp.c b/src/mms/iso_cotp/cotp.c
index 68ce1c1f..efd852e5 100644
--- a/src/mms/iso_cotp/cotp.c
+++ b/src/mms/iso_cotp/cotp.c
@@ -763,10 +763,12 @@ CotpConnection_readToTpktBuffer(CotpConnection* self)
 
 exit_closed:
     if (DEBUG_COTP) printf("TPKT: socket closed or socket error\n");
+    self->readBuffer->size = 0;
     return TPKT_ERROR;
 
 exit_error:
     if (DEBUG_COTP) printf("TPKT: Error parsing message\n");
+    self->readBuffer->size = 0;
     return TPKT_ERROR;
 
 exit_waiting: