diff --git a/src/emc/task/taskclass.cc b/src/emc/task/taskclass.cc
index c657448c79f..25dc5d47fca 100644
--- a/src/emc/task/taskclass.cc
+++ b/src/emc/task/taskclass.cc
@@ -587,14 +587,15 @@ int Task::emcToolSetOffset(int idx, int toolno, const EmcPose& offset, double di
     if (0 != tooldata_save(tooltable_filename)) {
         emcioStatus.status = RCS_STATUS::ERROR;
     }
-    //TODO
-    // if (io_db_mode == DB_ACTIVE) {
-    //     int pno = idx; // for random_toolchanger
-    //     if (!random_toolchanger) { pno = tdata.pocketno; }
-    //     if (tooldata_db_notify(TOOL_OFFSET,toolno,pno,tdata)) {
-    //         UNEXPECTED_MSG;
-    //     }
-    // }
+    if (db_mode == tooldb_t::DB_ACTIVE) {
+        // tooldata_save() does not write tool table entries in db mode,
+        // so the db_program must be notified to persist the new offsets
+        int pno = idx; // for random_toolchanger
+        if (!random_toolchanger) { pno = tdata.pocketno; }
+        if (tooldata_db_notify(TOOL_OFFSET,toolno,pno,tdata)) {
+            UNEXPECTED_MSG;
+        }
+    }
 
     return 0;
 }
diff --git a/tests/tooldb/db-g10-offset/.gitignore b/tests/tooldb/db-g10-offset/.gitignore
new file mode 100644
index 00000000000..211e02568a8
--- /dev/null
+++ b/tests/tooldb/db-g10-offset/.gitignore
@@ -0,0 +1,2 @@
+db_tools.txt
+db_cmds.log
diff --git a/tests/tooldb/db-g10-offset/README b/tests/tooldb/db-g10-offset/README
new file mode 100644
index 00000000000..e22c5da186c
--- /dev/null
+++ b/tests/tooldb/db-g10-offset/README
@@ -0,0 +1,6 @@
+Verify that tool offsets set with G10 L1/L10/L11 are persisted when an
+[EMCIO]DB_PROGRAM is configured.
+
+In db mode with a nonrandom toolchanger no tool table file is written, so the
+db program must be notified of the new offsets ('p' command).  Without that
+notification the offsets only live in memory and are lost on the next start.
diff --git a/tests/tooldb/db-g10-offset/base.inc b/tests/tooldb/db-g10-offset/base.inc
new file mode 100644
index 00000000000..70e31728ae5
--- /dev/null
+++ b/tests/tooldb/db-g10-offset/base.inc
@@ -0,0 +1,98 @@
+[EMC]
+# The version string for this INI file.
+VERSION = 1.1
+DEBUG = 0x0
+
+[RS274NGC]
+PARAMETER_FILE = sim.var
+
+[EMCMOT]
+EMCMOT = motmod
+COMM_TIMEOUT = 4.0
+BASE_PERIOD = 0
+SERVO_PERIOD = 1000000
+
+[TASK]
+TASK = milltask
+CYCLE_TIME = 0.001
+
+[HAL]
+# the library file provides the estop and toolchange loopbacks needed here
+HALFILE = LIB:core_sim.hal
+
+[TRAJ]
+NO_FORCE_HOMING=1
+COORDINATES = XYZ
+HOME =                  0 0 0
+LINEAR_UNITS =          inch
+ANGULAR_UNITS =         degree
+DEFAULT_LINEAR_VELOCITY =      1.2
+MAX_LINEAR_ACCELERATION =      123.45
+MAX_LINEAR_VELOCITY =          45.67
+
+[EMCIO]
+# no TOOL_TABLE: tool data is provided by the db program
+TOOL_CHANGE_QUILL_UP = 1
+RANDOM_TOOLCHANGER = 0
+DB_PROGRAM = ./db_test.py
+
+[KINS]
+KINEMATICS = trivkins coordinates=XYZ
+JOINTS = 3
+
+[AXIS_X]
+MIN_LIMIT = -40.0
+MAX_LIMIT = 40.0
+MAX_VELOCITY = 4
+MAX_ACCELERATION = 1000.0
+
+[JOINT_0]
+TYPE =             LINEAR
+HOME =             0.000
+MAX_VELOCITY =     4
+MAX_ACCELERATION = 1000.0
+BACKLASH =         0.000
+INPUT_SCALE =      4000
+OUTPUT_SCALE =     1.000
+MIN_LIMIT =        -40.0
+MAX_LIMIT =        40.0
+FERROR =           0.050
+MIN_FERROR =       0.010
+
+[AXIS_Y]
+MIN_LIMIT = -40.0
+MAX_LIMIT = 40.0
+MAX_VELOCITY = 4
+MAX_ACCELERATION = 1000.0
+
+[JOINT_1]
+TYPE =             LINEAR
+HOME =             0.000
+MAX_VELOCITY =     4
+MAX_ACCELERATION = 1000.0
+BACKLASH =         0.000
+INPUT_SCALE =      4000
+OUTPUT_SCALE =     1.000
+MIN_LIMIT =        -40.0
+MAX_LIMIT =        40.0
+FERROR =           0.050
+MIN_FERROR =       0.010
+
+[AXIS_Z]
+MIN_LIMIT = -40.0
+MAX_LIMIT = 40.0
+MAX_VELOCITY = 4
+MAX_ACCELERATION = 1000.0
+
+[JOINT_2]
+TYPE =             LINEAR
+HOME =             0.0
+MAX_VELOCITY =     4
+MAX_ACCELERATION = 1000.0
+BACKLASH =         0.000
+INPUT_SCALE =      4000
+OUTPUT_SCALE =     1.000
+MIN_LIMIT =        -40.0
+MAX_LIMIT =        40.0
+FERROR =           0.050
+MIN_FERROR =       0.010
diff --git a/tests/tooldb/db-g10-offset/checkresult b/tests/tooldb/db-g10-offset/checkresult
new file mode 100755
index 00000000000..24dc9aa53e3
--- /dev/null
+++ b/tests/tooldb/db-g10-offset/checkresult
@@ -0,0 +1,2 @@
+#!/bin/sh
+exit 0 # test failure is indicated by test.sh exit value
diff --git a/tests/tooldb/db-g10-offset/db_test.py b/tests/tooldb/db-g10-offset/db_test.py
new file mode 100755
index 00000000000..7cfef350941
--- /dev/null
+++ b/tests/tooldb/db-g10-offset/db_test.py
@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+# Minimal [EMCIO]DB_PROGRAM used by this test.
+# Tool data is kept in a flat file (db_tools.txt) so that it survives a
+# restart of LinuxCNC, and every received command is appended to db_cmds.log.
+# Note: stdout is the pipe to LinuxCNC, so logging goes to a file.
+
+import os
+
+from tooldb import tooldb_callbacks
+from tooldb import tooldb_tools
+from tooldb import tooldb_loop
+
+savefile = "db_tools.txt"
+logfile  = "db_cmds.log"
+
+initial_tools = {
+    1: "T1 P1 D0.1 Z0.5",
+    2: "T2 P2 D0.2 Z1.5",
+    3: "T3 P3 D0.3 Z2.5",
+}
+
+tools = {}
+
+def log(msg):
+    with open(logfile,"a") as f:
+        f.write("%s\n"%msg)
+
+def save():
+    with open(savefile,"w") as f:
+        for tno in sorted(tools):
+            f.write("%s\n"%tools[tno])
+
+def load():
+    if not os.path.exists(savefile):
+        tools.update(initial_tools)
+        save()
+        return
+    with open(savefile) as f:
+        for line in f:
+            line = line.strip()
+            if not line: continue
+            tools[toolno_of(line)] = line
+
+def toolno_of(toolline):
+    for item in toolline.upper().split():
+        if item.startswith("T"): return int(item[1:])
+    raise ValueError("no toolno in <%s>"%toolline)
+
+def merge(toolline,params):
+    # apply the letter parameters of params to toolline
+    D = dict((item[0],item[1:]) for item in toolline.upper().split())
+    for item in params.upper().split():
+        if item.startswith(";"): break
+        D[item[0]] = item[1:]
+    letters = ["T","P"] + sorted(set(D) - set(["T","P"]))
+    return " ".join("%s%s"%(letter,D[letter]) for letter in letters)
+
+#   'g' interface command
+def get_tool(tno):
+    log("g %s"%tools[tno])
+    return tools[tno]
+
+#   'p' interface command
+def put_tool(tno,params):
+    log("p %s"%params)
+    tools[tno] = merge(tools.get(tno,"T%d P%d"%(tno,tno)),params)
+    save()
+
+#   'l' interface command
+def load_spindle(tno,params):
+    log("l %s"%params)
+
+#   'u' interface command
+def unload_spindle(tno,params):
+    log("u %s"%params)
+
+load()
+tooldb_callbacks(get_tool,put_tool,load_spindle,unload_spindle)
+tooldb_tools(sorted(tools))
+tooldb_loop()
diff --git a/tests/tooldb/db-g10-offset/dbtest_lib.py b/tests/tooldb/db-g10-offset/dbtest_lib.py
new file mode 100644
index 00000000000..fbb6e18af10
--- /dev/null
+++ b/tests/tooldb/db-g10-offset/dbtest_lib.py
@@ -0,0 +1,82 @@
+# helpers shared by the ui scripts of this test
+
+import sys
+import time
+
+import linuxcnc
+
+savefile = "db_tools.txt"
+
+
+def wait_for_linuxcnc_startup(status, timeout=10.0):
+    """Poll the Status buffer waiting for it to look initialized, rather
+    than just allocated (all-zero)."""
+    start_time = time.time()
+    while time.time() - start_time < timeout:
+        status.poll()
+        if (status.angular_units == 0.0) \
+            or (status.axis_mask == 0) \
+            or (status.cycle_time == 0.0) \
+            or (status.exec_state != linuxcnc.EXEC_DONE) \
+            or (status.interp_state != linuxcnc.INTERP_IDLE) \
+            or (status.inpos is False) \
+            or (status.linear_units == 0.0) \
+            or (status.max_acceleration == 0.0) \
+            or (status.max_velocity == 0.0) \
+            or (status.program_units == 0.0) \
+            or (status.rapidrate == 0.0) \
+            or (status.state != linuxcnc.RCS_DONE) \
+            or (status.task_state != linuxcnc.STATE_ESTOP):
+            time.sleep(0.1)
+        else:
+            return
+    raise RuntimeError("timeout waiting for linuxcnc startup")
+
+
+def start_machine():
+    c = linuxcnc.command()
+    s = linuxcnc.stat()
+    wait_for_linuxcnc_startup(s)
+    c.state(linuxcnc.STATE_ESTOP_RESET)
+    c.state(linuxcnc.STATE_ON)
+    c.home(-1)
+    c.wait_complete()
+    c.mode(linuxcnc.MODE_MDI)
+    c.wait_complete()
+    return (c, s)
+
+
+def fail(msg):
+    print("FAIL: %s" % msg)
+    sys.exit(1)
+
+
+def check(what, got, expected):
+    if abs(got - expected) > 1e-6:
+        fail("%s: expected %.6f, got %.6f" % (what, expected, got))
+    print("ok: %s = %.6f" % (what, got))
+
+
+def tool_table_zoffset(s, idx):
+    s.poll()
+    return s.tool_table[idx].zoffset
+
+
+def db_zoffset(toolno, timeout=0):
+    """Z offset recorded by the db program for toolno, or None."""
+    deadline = time.time() + timeout
+    while True:
+        try:
+            with open(savefile) as f:
+                for line in f:
+                    items = line.upper().split()
+                    if "T%d" % toolno not in items:
+                        continue
+                    for item in items:
+                        if item.startswith("Z"):
+                            return float(item[1:])
+        except IOError:
+            pass
+        if time.time() >= deadline:
+            return None
+        time.sleep(0.1)
diff --git a/tests/tooldb/db-g10-offset/test-ui.py b/tests/tooldb/db-g10-offset/test-ui.py
new file mode 100755
index 00000000000..28cfded060b
--- /dev/null
+++ b/tests/tooldb/db-g10-offset/test-ui.py
@@ -0,0 +1,50 @@
+#!/usr/bin/env python3
+
+# With an [EMCIO]DB_PROGRAM configured and a nonrandom toolchanger, no tool
+# table file is written, so G10 L1/L10/L11 offsets are persisted only if the
+# db program is notified ('p' command).
+
+import sys
+
+from dbtest_lib import start_machine, check, fail, tool_table_zoffset, db_zoffset
+
+(c, s) = start_machine()
+
+# initial values come from the db program
+check("tool 3 zoffset at startup", tool_table_zoffset(s, 3), 2.5)
+check("db zoffset for tool 3 at startup", db_zoffset(3), 2.5)
+
+# 1) G10 L1 on a tool that is not in the spindle
+c.mdi("G10 L1 P3 Z-12.345")
+c.wait_complete()
+
+check("tool 3 zoffset after G10 L1", tool_table_zoffset(s, 3), -12.345)
+
+got = db_zoffset(3, timeout=5)
+if got is None:
+    fail("db program was not notified of the G10 L1 offset for tool 3")
+check("db zoffset for tool 3 after G10 L1", got, -12.345)
+
+# 2) G10 L1 on the tool that is in the spindle
+c.mdi("T2 M6")
+c.wait_complete()
+s.poll()
+if s.tool_in_spindle != 2:
+    fail("expected tool 2 in spindle, got %d" % s.tool_in_spindle)
+
+c.mdi("G10 L1 P2 Z-6.789")
+c.wait_complete()
+
+check("tool 2 zoffset after G10 L1", tool_table_zoffset(s, 2), -6.789)
+check("spindle zoffset after G10 L1", tool_table_zoffset(s, 0), -6.789)
+
+got = db_zoffset(2, timeout=5)
+if got is None:
+    fail("db program was not notified of the G10 L1 offset for tool 2")
+check("db zoffset for tool 2 after G10 L1", got, -6.789)
+
+# unload the tool so the db program sees a clean shutdown
+c.mdi("T0 M6")
+c.wait_complete()
+
+sys.exit(0)
diff --git a/tests/tooldb/db-g10-offset/test.ini b/tests/tooldb/db-g10-offset/test.ini
new file mode 100644
index 00000000000..2f2a135c371
--- /dev/null
+++ b/tests/tooldb/db-g10-offset/test.ini
@@ -0,0 +1,5 @@
+# apply G10 L1 tool offsets with an [EMCIO]DB_PROGRAM configured
+[DISPLAY]
+DISPLAY = ./test-ui.py
+
+#INCLUDE base.inc
diff --git a/tests/tooldb/db-g10-offset/test.sh b/tests/tooldb/db-g10-offset/test.sh
new file mode 100755
index 00000000000..d67ba664c8d
--- /dev/null
+++ b/tests/tooldb/db-g10-offset/test.sh
@@ -0,0 +1,11 @@
+#!/bin/bash
+set -x
+set -e
+
+rm -f sim.var* db_tools.txt db_cmds.log
+
+# run 1: apply G10 L1 offsets (db program creates db_tools.txt)
+linuxcnc -r test.ini
+
+# run 2: the offsets must be restored from the db program
+linuxcnc -r verify.ini
diff --git a/tests/tooldb/db-g10-offset/verify-ui.py b/tests/tooldb/db-g10-offset/verify-ui.py
new file mode 100755
index 00000000000..99124db2143
--- /dev/null
+++ b/tests/tooldb/db-g10-offset/verify-ui.py
@@ -0,0 +1,16 @@
+#!/usr/bin/env python3
+
+# Second run: the tool data now comes from the db program, and must carry the
+# offsets written by test-ui.py in the previous run.
+
+import sys
+
+from dbtest_lib import start_machine, check, tool_table_zoffset
+
+(c, s) = start_machine()
+
+check("tool 3 zoffset after restart", tool_table_zoffset(s, 3), -12.345)
+check("tool 2 zoffset after restart", tool_table_zoffset(s, 2), -6.789)
+check("tool 1 zoffset after restart", tool_table_zoffset(s, 1), 0.5)
+
+sys.exit(0)
diff --git a/tests/tooldb/db-g10-offset/verify.ini b/tests/tooldb/db-g10-offset/verify.ini
new file mode 100644
index 00000000000..ac5c4245e00
--- /dev/null
+++ b/tests/tooldb/db-g10-offset/verify.ini
@@ -0,0 +1,5 @@
+# restart: the offsets applied by test.ini must come back from the db program
+[DISPLAY]
+DISPLAY = ./verify-ui.py
+
+#INCLUDE base.inc