diff --git a/test-linuxcnc-rs274-native.sh b/test-linuxcnc-rs274-native.sh
index 7bc5f45..cd84cc6 100755
--- a/test-linuxcnc-rs274-native.sh
+++ b/test-linuxcnc-rs274-native.sh
@@ -1144,6 +1144,9 @@ for case in "${nurbs_error_cases[@]}"; do
     fi
     grep -Fq "$expected" "$output_dir/cnc_sim_linuxcnc_$fixture.err"
 done
+# Source basis: LinuxCNC src/emc/rs274ngc/interp_convert.cc convert_setup()
+# stores G10 L2 U/V/W through PROGRAM_TO_USER_LEN, and
+# convert_coordinate_system() emits them through SET_G5X_OFFSET.
 cp "$base_var_file" "$var_file"
 CNC_SIM_RS274_VAR="$var_file" "$build_dir/linuxcnc_rs274_dump" tests/gcode/linuxcnc_coordinate_offsets.ngc >"$output_dir/cnc_sim_linuxcnc_coordinate_offsets.json"
 cp "$base_var_file" "$var_file"
@@ -2944,7 +2947,10 @@ if not any(
     event["tool"] == 1 and
     event["start"]["x"] == 12.5 and
     event["start"]["y"] == -3 and
-    event["start"]["z"] == 4
+    event["start"]["z"] == 4 and
+    event["start"]["u"] == 7 and
+    event["start"]["v"] == 8 and
+    event["start"]["w"] == 9
     for event in g5x
 ):
     raise SystemExit("missing G10 L2 G5X offset event")
diff --git a/test-linuxcnc-source-link.sh b/test-linuxcnc-source-link.sh
index 04ff903..7888076 100755
--- a/test-linuxcnc-source-link.sh
+++ b/test-linuxcnc-source-link.sh
@@ -1802,6 +1802,9 @@ done
 CNC_SIM_RS274_FILE_MODE=1 CNC_SIM_RS274_VAR="$var_file" \
     "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_g76only.ngc \
     >"$output_dir/cnc_sim_linuxcnc_source_g76only.json"
+# Source basis: LinuxCNC src/emc/rs274ngc/interp_convert.cc convert_setup()
+# stores G10 L2 U/V/W through PROGRAM_TO_USER_LEN, and
+# convert_coordinate_system() emits them through SET_G5X_OFFSET.
 cp "$base_var_file" "$var_file"
 CNC_SIM_RS274_VAR="$var_file" \
     "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_coordinate_offsets.ngc \
@@ -3972,7 +3975,10 @@ if not any(
     event["tool"] == 1 and
     event["start"]["x"] == 12.5 and
     event["start"]["y"] == -3 and
-    event["start"]["z"] == 4
+    event["start"]["z"] == 4 and
+    event["start"]["u"] == 7 and
+    event["start"]["v"] == 8 and
+    event["start"]["w"] == 9
     for event in g5x
 ):
     raise SystemExit("missing source-linked G10 L2 G5X offset event")
diff --git a/tests/gcode/linuxcnc_coordinate_offsets.ngc b/tests/gcode/linuxcnc_coordinate_offsets.ngc
index 7274e0f..e420dfb 100644
--- a/tests/gcode/linuxcnc_coordinate_offsets.ngc
+++ b/tests/gcode/linuxcnc_coordinate_offsets.ngc
@@ -1,5 +1,5 @@
 G21 G90 G17
-G10 L2 P1 X12.5 Y-3 Z4 R30
+G10 L2 P1 X12.5 Y-3 Z4 U7 V8 W9 R30
 G92 X1 Y2 Z3
 G92.1
 M30