diff --git a/hio/lib/err.c b/hio/lib/err.c
index 2e813aa..2ef28e4 100644
--- a/hio/lib/err.c
+++ b/hio/lib/err.c
@@ -49,7 +49,7 @@ static hio_ooch_t errstr_20[] = {'I', '/', 'O', ' ', 'e', 'r', 'r', 'o', 'r', '\
 static hio_ooch_t errstr_21[] = {'e', 'n', 'c', 'o', 'd', 'i', 'n', 'g', ' ', 'c', 'o', 'n', 'v', 'e', 'r', 's', 'i', 'o', 'n', ' ', 'e', 'r', 'r', 'o', 'r', '\0' };
 static hio_ooch_t errstr_22[] = {'i', 'n', 's', 'u', 'f', 'f', 'i', 'c', 'i', 'e', 'n', 't', ' ', 'd', 'a', 't', 'a', ' ', 'f', 'o', 'r', ' ', 'e', 'n', 'c', 'o', 'd', 'i', 'n', 'g', ' ', 'c', 'o', 'n', 'v', 'e', 'r', 's', 'i', 'o', 'n', '\0' };
 static hio_ooch_t errstr_23[] = {'b', 'u', 'f', 'f', 'e', 'r', ' ', 'f', 'u', 'l', 'l', '\0' };
-static hio_ooch_t errstr_24[] = {'n', 'o', 't', ' ', 'c', 'o', 'n', 'n', 'e', 'c', 't', 'e', 'd', '\0' };
+static hio_ooch_t errstr_24[] = {'c', 'o', 'n', 'n', 'e', 'c', 't', 'i', 'o', 'n', ' ', 'l', 'o', 's', 't', '\0' };
 static hio_ooch_t errstr_25[] = {'c', 'o', 'n', 'n', 'e', 'c', 't', 'i', 'o', 'n', ' ', 'r', 'e', 'f', 'u', 's', 'e', 'd', '\0' };
 static hio_ooch_t errstr_26[] = {'c', 'o', 'n', 'n', 'e', 'c', 't', 'i', 'o', 'n', ' ', 'r', 'e', 's', 'e', 't', '\0' };
 static hio_ooch_t errstr_27[] = {'n', 'o', ' ', 'c', 'a', 'p', 'a', 'b', 'i', 'l', 'i', 't', 'y', '\0' };
diff --git a/hio/lib/hio.h b/hio/lib/hio.h
index 50d5642..af2a9cc 100644
--- a/hio/lib/hio.h
+++ b/hio/lib/hio.h
@@ -99,7 +99,7 @@ enum hio_errnum_t
 	HIO_EECMORE,  /**< insufficient data for encoding conversion */
 	HIO_EBUFFULL, /**< buffer full */
 
-	HIO_ENOTCON,  /**< not connected */
+	HIO_ECONLOST, /**< connection lost */
 	HIO_ECONRF,   /**< connection refused */
 	HIO_ECONRS,   /**< connection reset */
 	HIO_ENOCAPA,  /**< no capability */
diff --git a/hio/lib/mar-cli.c b/hio/lib/mar-cli.c
index 1c9cf0e..47f126e 100644
--- a/hio/lib/mar-cli.c
+++ b/hio/lib/mar-cli.c
@@ -577,7 +577,7 @@ int hio_svc_marc_querywithbchars (hio_svc_marc_t* marc, hio_oow_t flagged_sid, h
 				return -1;
 			}
 
-			/* the underlying socket of the device may get disconnected.
+			/* the underlying socket of the device might have gotten disconnected.
 			 * in such a case, keep the enqueued query with sq->sent 0
 			 * and defer actual sending and processing */
 		}
diff --git a/hio/lib/mar.c b/hio/lib/mar.c
index bea5ebf..8fb5ae1 100644
--- a/hio/lib/mar.c
+++ b/hio/lib/mar.c
@@ -28,13 +28,19 @@
 #if 0
 #include <mariadb/mysql.h>
 #include <mariadb/errmsg.h>
+#include <mariadb/mysqld_error.h>
 #else
 #include <mysql.h>
 #include <errmsg.h>
+#include <mysqld_error.h>
 #endif
 
 #include <sys/socket.h>
 
+#if !defined(ER_CONNECTION_KILLED)
+#	define ER_CONNECTION_KILLED (1927)
+#endif
+
 /* ========================================================================= */
 
 static int dev_mar_make (hio_dev_t* dev, void* ctx)
@@ -296,12 +302,14 @@ static int dev_mar_ioctl (hio_dev_t* dev, int cmd, void* arg)
 				if (err) 
 				{
 					/* but there is an error */
-					if (err == 1) err = mysql_errno(rdev->hnd);
+					if (err == 1 || err == -1) err = mysql_errno(rdev->hnd);
 
-					hio_seterrbfmt (hio, HIO_ESYSERR, "%hs", mysql_error(rdev->hnd));
-					if (err == CR_SERVER_LOST || err == CR_SERVER_GONE_ERROR)
+					hio_seterrbfmt (hio, HIO_ESYSERR, "%hs [code=%d]", mysql_error(rdev->hnd), err);
+					if (err == CR_SERVER_LOST || err == CR_SERVER_GONE_ERROR || err == CR_COMMANDS_OUT_OF_SYNC || err == ER_CONNECTION_KILLED)
 					{
-						/* the underlying socket must have gotten closed by mysql_real_query_start() */
+						/* the underlying socket is closed by the mysql client library when this happens.
+						 * so the mysql_get_socket(rdev->hnd) afterwards is never reliable */
+
 						const hio_ooch_t* prev_errmsg;
 						prev_errmsg = hio_backuperrmsg(hio);
 
@@ -312,7 +320,7 @@ static int dev_mar_ioctl (hio_dev_t* dev, int cmd, void* arg)
 
 						watch_mysql (rdev, 0);
 						hio_dev_mar_halt (rdev); /* i can't keep this device alive regardless of the caller's post-action */
-						hio_seterrbfmt (hio, HIO_ENOTCON, "%js", prev_errmsg);
+						hio_seterrbfmt (hio, HIO_ECONLOST, "%js", prev_errmsg);
 					}
 					return -1;
 				}
@@ -487,14 +495,14 @@ static int dev_evcb_mar_ready (hio_dev_t* dev, int events)
 					if (err)
 					{
 						/* query send failure */
-						if (err == 1) err = mysql_errno(rdev->hnd); /* err is set to 1 by mariadb-connector-c 3.1 as of this writing. let me work around it by fetching the error code */
+						if (err == 1 || err == -1) err = mysql_errno(rdev->hnd); /* err is set to 1 by mariadb-connector-c 3.1 as of this writing. let me work around it by fetching the error code */
 
-						if (err == CR_SERVER_LOST || err == CR_SERVER_GONE_ERROR)
+						if (err == CR_SERVER_LOST || err == CR_SERVER_GONE_ERROR || err == CR_COMMANDS_OUT_OF_SYNC || err == ER_CONNECTION_KILLED)
 						{
 							/*
 							preserving the error information here isn't very useful because 
 							the info won't survive until on_disconnect() is called...
-							hio_seterrbfmt (hio, HIO_ENOTCON, "%hs", mysql_error(rdev->hnd));
+							hio_seterrbfmt (hio, HIO_ECONLOST, "%hs", mysql_error(rdev->hnd));
 							*/
 
 							rdev->broken = 1;