diff --git a/test-linuxcnc-rs274-native.sh b/test-linuxcnc-rs274-native.sh
index c081a03..f220384 100755
--- a/test-linuxcnc-rs274-native.sh
+++ b/test-linuxcnc-rs274-native.sh
@@ -495,10 +495,11 @@ for case in "${threading_check_error_cases[@]}"; do
     grep -Fq "$expected" "$output_dir/cnc_sim_linuxcnc_$fixture.err"
 done
 # Source basis: LinuxCNC src/emc/rs274ngc/interp_convert.cc
-# convert_straight() and convert_threading_cycle() reject invalid
+# convert_arc(), convert_straight(), and convert_threading_cycle() reject invalid
 # feed/spindle state, spindle selectors, rotary-axis motion, and G76 I/J/K
-# geometry before issuing straight or synchronized threading motion.
+# geometry before issuing arc, straight, or synchronized threading motion.
 threading_convert_error_cases=(
+    "linuxcnc_arc_inverse_time_missing_f_error|F word missing with inverse time arc move"
     "linuxcnc_g1_zero_feed_error|Cannot do g1 with zero feed rate"
     "linuxcnc_g1_inverse_time_missing_f_error|F word missing with inverse time g1 move"
     "linuxcnc_g33_stopped_spindle_error|Spindle not turning in G33"
diff --git a/test-linuxcnc-source-link.sh b/test-linuxcnc-source-link.sh
index 9f6ad41..d7ce3af 100755
--- a/test-linuxcnc-source-link.sh
+++ b/test-linuxcnc-source-link.sh
@@ -1079,10 +1079,11 @@ for case in "${threading_check_error_cases[@]}"; do
     grep -Fq "$expected" "$output_dir/cnc_sim_linuxcnc_source_$fixture.err"
 done
 # Source basis: LinuxCNC src/emc/rs274ngc/interp_convert.cc
-# convert_straight() and convert_threading_cycle() reject invalid
+# convert_arc(), convert_straight(), and convert_threading_cycle() reject invalid
 # feed/spindle state, spindle selectors, rotary-axis motion, and G76 I/J/K
-# geometry before issuing straight or synchronized threading motion.
+# geometry before issuing arc, straight, or synchronized threading motion.
 threading_convert_error_cases=(
+    "linuxcnc_arc_inverse_time_missing_f_error|F word missing with inverse time arc move"
     "linuxcnc_g1_zero_feed_error|Cannot do g1 with zero feed rate"
     "linuxcnc_g1_inverse_time_missing_f_error|F word missing with inverse time g1 move"
     "linuxcnc_g33_stopped_spindle_error|Spindle not turning in G33"
diff --git a/tests/gcode/linuxcnc_arc_inverse_time_missing_f_error.ngc b/tests/gcode/linuxcnc_arc_inverse_time_missing_f_error.ngc
new file mode 100644
index 0000000..67a622c
--- /dev/null
+++ b/tests/gcode/linuxcnc_arc_inverse_time_missing_f_error.ngc
@@ -0,0 +1,4 @@
+G21 G90 G17
+G0 X0 Y0
+G93
+G2 X1 Y0 R0.5