diff --git a/test-linuxcnc-source-link.sh b/test-linuxcnc-source-link.sh
index 8d9785a..e296985 100755
--- a/test-linuxcnc-source-link.sh
+++ b/test-linuxcnc-source-link.sh
@@ -576,6 +576,29 @@ for case in "${polar_coordinate_error_cases[@]}"; do
     fi
     grep -Fq "$expected" "$output_dir/cnc_sim_linuxcnc_source_$fixture.err"
 done
+# Source basis: LinuxCNC src/emc/rs274ngc/interp_internal.cc
+# enhance_block() assigns motion_to_be and rejects invalid axis use with G80,
+# missing axes for G52/G92 or motion codes, bare axis words without active
+# motion, and modal-0 G codes that consume axis values on a motion block.
+enhance_block_error_cases=(
+    "linuxcnc_g80_axis_error|Cannot use axis values with g80"
+    "linuxcnc_g52_missing_axis_error|All axes missing with g52 or g92"
+    "linuxcnc_g92_missing_axis_error|All axes missing with g52 or g92"
+    "linuxcnc_motion_missing_axis_error|All axes missing with motion code"
+    "linuxcnc_axis_without_motion_error|Cannot use axis values without a g code that uses them"
+    "linuxcnc_motion_with_g92_axis_error|Cannot use two g codes that both use axis values"
+)
+for case in "${enhance_block_error_cases[@]}"; do
+    fixture=${case%%|*}
+    expected=${case#*|}
+    if CNC_SIM_RS274_VAR="$var_file" \
+        "$build_dir/linuxcnc_rs274_source_dump" "tests/gcode/$fixture.ngc" \
+        >"$output_dir/cnc_sim_linuxcnc_source_$fixture.json" 2>"$output_dir/cnc_sim_linuxcnc_source_$fixture.err"; then
+        echo "expected $fixture.ngc to fail" >&2
+        exit 1
+    fi
+    grep -Fq "$expected" "$output_dir/cnc_sim_linuxcnc_source_$fixture.err"
+done
 CNC_SIM_RS274_VAR="$var_file" \
     "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_predefined_positions.ngc \
     >"$output_dir/cnc_sim_linuxcnc_source_predefined_positions.json"
diff --git a/test-native.sh b/test-native.sh
index 1096b8c..cbaf2c6 100755
--- a/test-native.sh
+++ b/test-native.sh
@@ -147,6 +147,8 @@ grep -F 'tests/gcode/linuxcnc_lathe_diameter_g76.ngc' docs/linuxcnc-porting.md >
 grep -F 'missing source-linked G7 diameter-mode G76 final threading pass' test-linuxcnc-source-link.sh >/dev/null
 grep -F 'read_atsign()' test-linuxcnc-source-link.sh >/dev/null
 grep -F 'tests/gcode/linuxcnc_polar_coordinates.ngc' test-linuxcnc-source-link.sh >/dev/null
+grep -F 'enhance_block() assigns motion_to_be' test-linuxcnc-source-link.sh >/dev/null
+grep -F 'linuxcnc_g80_axis_error|Cannot use axis values with g80' test-linuxcnc-source-link.sh >/dev/null
 grep -F 'lookup_named_param()' test-linuxcnc-rs274-native.sh >/dev/null
 grep -F 'tests/gcode/linuxcnc_readonly_named_parameters.ngc' docs/linuxcnc-porting.md >/dev/null
 grep -F 'rs274ngc_pre.cc ini_load() consumes INI_FILE_NAME' test-web-wasm-node-smoke.cjs >/dev/null
diff --git a/tests/gcode/linuxcnc_axis_without_motion_error.ngc b/tests/gcode/linuxcnc_axis_without_motion_error.ngc
new file mode 100644
index 0000000..f36fdd8
--- /dev/null
+++ b/tests/gcode/linuxcnc_axis_without_motion_error.ngc
@@ -0,0 +1,3 @@
+G21 G90 G17
+X1
+M30
diff --git a/tests/gcode/linuxcnc_g52_missing_axis_error.ngc b/tests/gcode/linuxcnc_g52_missing_axis_error.ngc
new file mode 100644
index 0000000..0b40266
--- /dev/null
+++ b/tests/gcode/linuxcnc_g52_missing_axis_error.ngc
@@ -0,0 +1,3 @@
+G21 G90 G17
+G52
+M30
diff --git a/tests/gcode/linuxcnc_g80_axis_error.ngc b/tests/gcode/linuxcnc_g80_axis_error.ngc
new file mode 100644
index 0000000..4b622d5
--- /dev/null
+++ b/tests/gcode/linuxcnc_g80_axis_error.ngc
@@ -0,0 +1,3 @@
+G21 G90 G17
+G80 X1
+M30
diff --git a/tests/gcode/linuxcnc_g92_missing_axis_error.ngc b/tests/gcode/linuxcnc_g92_missing_axis_error.ngc
new file mode 100644
index 0000000..0f30a1d
--- /dev/null
+++ b/tests/gcode/linuxcnc_g92_missing_axis_error.ngc
@@ -0,0 +1,3 @@
+G21 G90 G17
+G92
+M30
diff --git a/tests/gcode/linuxcnc_motion_missing_axis_error.ngc b/tests/gcode/linuxcnc_motion_missing_axis_error.ngc
new file mode 100644
index 0000000..99f3bcb
--- /dev/null
+++ b/tests/gcode/linuxcnc_motion_missing_axis_error.ngc
@@ -0,0 +1,3 @@
+G21 G90 G17
+G81 F100
+M30
diff --git a/tests/gcode/linuxcnc_motion_with_g92_axis_error.ngc b/tests/gcode/linuxcnc_motion_with_g92_axis_error.ngc
new file mode 100644
index 0000000..82f3dd5
--- /dev/null
+++ b/tests/gcode/linuxcnc_motion_with_g92_axis_error.ngc
@@ -0,0 +1,3 @@
+G21 G90 G17
+G1 G92 X1 F100
+M30