diff --git a/test-linuxcnc-rs274-native.sh b/test-linuxcnc-rs274-native.sh
index 6b6ec7c..f8c8e94 100755
--- a/test-linuxcnc-rs274-native.sh
+++ b/test-linuxcnc-rs274-native.sh
@@ -591,9 +591,10 @@ done
 CNC_SIM_RS274_VAR="$var_file" "$build_dir/linuxcnc_rs274_dump" tests/gcode/linuxcnc_canned_cycle.ngc >"$output_dir/cnc_sim_linuxcnc_canned_cycle.json"
 # Source basis: LinuxCNC src/emc/rs274ngc/interp_cycles.cc
 # convert_cycle() and the G73/G74/G82-G89 helpers validate canned-cycle
-# repeat counts, plane-specific axis/R words, Q/P requirements, and spindle
-# state before expanding cycles to Canon motion.
+# feed mode, repeat counts, plane-specific axis/R words, Q/P requirements,
+# and spindle state before expanding cycles to Canon motion.
 canned_cycle_error_cases=(
+    "linuxcnc_canned_cycle_inverse_time_error|Cannot use inverse time feed with canned cycles"
     "linuxcnc_canned_cycle_l0_error|Cannot do zero repeats of cycle"
     "linuxcnc_canned_cycle_missing_r_error|R clearance plane unspecified in cycle"
     "linuxcnc_canned_cycle_missing_z_error|Z value unspecified in xy plane canned cycle"
diff --git a/test-linuxcnc-source-link.sh b/test-linuxcnc-source-link.sh
index bf7e434..fb969af 100755
--- a/test-linuxcnc-source-link.sh
+++ b/test-linuxcnc-source-link.sh
@@ -366,6 +366,17 @@ done
 CNC_SIM_RS274_VAR="$var_file" \
     "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_canned_cycle.ngc \
     >"$output_dir/cnc_sim_linuxcnc_source_canned_cycle.json"
+# Source basis: LinuxCNC src/emc/rs274ngc/interp_cycles.cc
+# convert_cycle() rejects inverse-time feed mode before expanding canned
+# cycles through convert_cycle_xy()/yz()/zx().
+if CNC_SIM_RS274_VAR="$var_file" \
+    "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_canned_cycle_inverse_time_error.ngc \
+    >"$output_dir/cnc_sim_linuxcnc_source_canned_cycle_inverse_time_error.json" \
+    2>"$output_dir/cnc_sim_linuxcnc_source_canned_cycle_inverse_time_error.err"; then
+    echo "expected linuxcnc_canned_cycle_inverse_time_error.ngc to fail" >&2
+    exit 1
+fi
+grep -q "Cannot use inverse time feed with canned cycles" "$output_dir/cnc_sim_linuxcnc_source_canned_cycle_inverse_time_error.err"
 if CNC_SIM_RS274_VAR="$var_file" \
     "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_canned_cycle_l0_error.ngc \
     >"$output_dir/cnc_sim_linuxcnc_source_canned_cycle_l0_error.json" \
diff --git a/tests/gcode/linuxcnc_canned_cycle_inverse_time_error.ngc b/tests/gcode/linuxcnc_canned_cycle_inverse_time_error.ngc
new file mode 100644
index 0000000..c02d6b7
--- /dev/null
+++ b/tests/gcode/linuxcnc_canned_cycle_inverse_time_error.ngc
@@ -0,0 +1,4 @@
+G21 G90 G17
+F100
+G93
+G81 X1 Z-1 R1