diff --git a/test-linuxcnc-rs274-native.sh b/test-linuxcnc-rs274-native.sh
index a3bd422..e643577 100755
--- a/test-linuxcnc-rs274-native.sh
+++ b/test-linuxcnc-rs274-native.sh
@@ -45,6 +45,7 @@ ini_named_parameter_file="$(pwd)/tests/gcode/linuxcnc_ini_named_parameter.ini"
 disable_g92_persistence_ini_file="$(pwd)/tests/gcode/linuxcnc_disable_g92_persistence.ini"
 disable_fanuc_style_sub_ini_file="$(pwd)/tests/gcode/linuxcnc_disable_fanuc_style_sub.ini"
 tight_arc_center_tolerance_ini_file="$(pwd)/tests/gcode/linuxcnc_tight_arc_center_tolerance.ini"
+g64_default_tolerances_ini_file="$(pwd)/tests/gcode/linuxcnc_g64_default_tolerances.ini"
 output_dir="$build_dir/outputs"
 mkdir -p "$output_dir"
 cp "$linuxcnc_root/tests/halui/jogging/sim.var" "$base_var_file"
@@ -596,6 +597,10 @@ CNC_SIM_RS274_VAR="$var_file" "$build_dir/linuxcnc_rs274_dump" tests/gcode/linux
 # convert_control_mode() sends G64 P through SET_MOTION_CONTROL_MODE()
 # and G64 Q through SET_NAIVECAM_TOLERANCE(), defaulting Q to P when Q is omitted.
 CNC_SIM_RS274_VAR="$var_file" "$build_dir/linuxcnc_rs274_dump" tests/gcode/linuxcnc_control_mode_tolerances.ngc >"$output_dir/cnc_sim_linuxcnc_control_mode_tolerances.json"
+# Source basis: LinuxCNC src/emc/rs274ngc/rs274ngc_pre.cc init reads
+# [RS274NGC] G64_DEFAULT_TOLERANCE/G64_DEFAULT_NAIVETOLERANCE, and
+# interp_convert.cc convert_control_mode() uses them when G64 omits P/Q.
+INI_FILE_NAME="$g64_default_tolerances_ini_file" CNC_SIM_RS274_VAR="$var_file" "$build_dir/linuxcnc_rs274_dump" tests/gcode/linuxcnc_g64_default_tolerances.ngc >"$output_dir/cnc_sim_linuxcnc_g64_default_tolerances.json"
 CNC_SIM_RS274_VAR="$var_file" "$build_dir/linuxcnc_rs274_dump" tests/gcode/linuxcnc_tool_length.ngc >"$output_dir/cnc_sim_linuxcnc_tool_length.json"
 CNC_SIM_RS274_VAR="$var_file" "$build_dir/linuxcnc_rs274_dump" tests/gcode/linuxcnc_dynamic_tool_length.ngc >"$output_dir/cnc_sim_linuxcnc_dynamic_tool_length.json"
 # Source basis: LinuxCNC src/emc/rs274ngc/interp_convert.cc
@@ -1616,6 +1621,19 @@ expected_control_mode_tolerance_states = [
 if control_mode_tolerance_states != expected_control_mode_tolerance_states:
     raise SystemExit(f"unexpected G64 P/Q control mode tolerance states: {control_mode_tolerance_states!r}")
 
+g64_default_tolerances = load("cnc_sim_linuxcnc_g64_default_tolerances.json")
+g64_default_tolerance_states = [
+    (event["line"], event["reserved"], event["feed"])
+    for event in g64_default_tolerances
+    if event["type"] == "comment" and event["reserved"] in {640, 641}
+]
+expected_g64_default_tolerance_states = [
+    (3, 640, 0.07),
+    (3, 641, 0.04),
+]
+if g64_default_tolerance_states != expected_g64_default_tolerance_states:
+    raise SystemExit(f"unexpected INI-backed G64 default tolerance states: {g64_default_tolerance_states!r}")
+
 tool_length = load("cnc_sim_linuxcnc_tool_length.json")
 if not any(
     event["type"] == "comment" and
@@ -3020,6 +3038,7 @@ echo "dumped $output_dir/cnc_sim_linuxcnc_program_end_m99.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_coolant.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_feed_modes.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_motion_modes.json"
+echo "dumped $output_dir/cnc_sim_linuxcnc_g64_default_tolerances.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_tool_length.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_dynamic_tool_length.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_canned_cycle.json"
diff --git a/test-linuxcnc-source-link.sh b/test-linuxcnc-source-link.sh
index 546e2ad..e1c5f49 100755
--- a/test-linuxcnc-source-link.sh
+++ b/test-linuxcnc-source-link.sh
@@ -178,6 +178,7 @@ ini_named_parameter_file="$(pwd)/tests/gcode/linuxcnc_ini_named_parameter.ini"
 disable_g92_persistence_ini_file="$(pwd)/tests/gcode/linuxcnc_disable_g92_persistence.ini"
 disable_fanuc_style_sub_ini_file="$(pwd)/tests/gcode/linuxcnc_disable_fanuc_style_sub.ini"
 tight_arc_center_tolerance_ini_file="$(pwd)/tests/gcode/linuxcnc_tight_arc_center_tolerance.ini"
+g64_default_tolerances_ini_file="$(pwd)/tests/gcode/linuxcnc_g64_default_tolerances.ini"
 multi_spindle_modes_file="$(pwd)/tests/gcode/linuxcnc_multi_spindle_modes.ini"
 multi_spindle_override_file="$(pwd)/tests/gcode/linuxcnc_multi_spindle_override.ini"
 multi_spindle_threading_file="$(pwd)/tests/gcode/linuxcnc_multi_spindle_threading.ini"
@@ -412,6 +413,12 @@ CNC_SIM_RS274_VAR="$var_file" \
 CNC_SIM_RS274_VAR="$var_file" \
     "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_control_mode_tolerances.ngc \
     >"$output_dir/cnc_sim_linuxcnc_source_control_mode_tolerances.json"
+# Source basis: LinuxCNC src/emc/rs274ngc/rs274ngc_pre.cc init reads
+# [RS274NGC] G64_DEFAULT_TOLERANCE/G64_DEFAULT_NAIVETOLERANCE, and
+# interp_convert.cc convert_control_mode() uses them when G64 omits P/Q.
+INI_FILE_NAME="$g64_default_tolerances_ini_file" CNC_SIM_RS274_VAR="$var_file" \
+    "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_g64_default_tolerances.ngc \
+    >"$output_dir/cnc_sim_linuxcnc_source_g64_default_tolerances.json"
 CNC_SIM_RS274_VAR="$var_file" \
     "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_tool_length.ngc \
     >"$output_dir/cnc_sim_linuxcnc_source_tool_length.json"
@@ -2217,6 +2224,19 @@ expected_control_mode_tolerance_states = [
 if control_mode_tolerance_states != expected_control_mode_tolerance_states:
     raise SystemExit(f"unexpected source-linked G64 P/Q control mode tolerance states: {control_mode_tolerance_states!r}")
 
+g64_default_tolerances = json.loads((OUTPUT_DIR / "cnc_sim_linuxcnc_source_g64_default_tolerances.json").read_text())
+g64_default_tolerance_states = [
+    (event["line"], event["reserved"], event["feed"])
+    for event in g64_default_tolerances
+    if event["type"] == "comment" and event["reserved"] in {640, 641}
+]
+expected_g64_default_tolerance_states = [
+    (3, 640, 0.07),
+    (3, 641, 0.04),
+]
+if g64_default_tolerance_states != expected_g64_default_tolerance_states:
+    raise SystemExit(f"unexpected source-linked INI-backed G64 default tolerance states: {g64_default_tolerance_states!r}")
+
 modal_state = json.loads((OUTPUT_DIR / "cnc_sim_linuxcnc_source_modal_state.json").read_text())
 if not any(
     event["type"] == "rapid" and
@@ -4046,6 +4066,7 @@ echo "dumped $output_dir/cnc_sim_linuxcnc_source_program_end_m99.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_source_coolant.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_source_feed_modes.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_source_motion_modes.json"
+echo "dumped $output_dir/cnc_sim_linuxcnc_source_g64_default_tolerances.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_source_tool_length.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_source_dynamic_tool_length.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_source_canned_cycle.json"
diff --git a/tests/gcode/linuxcnc_g64_default_tolerances.ini b/tests/gcode/linuxcnc_g64_default_tolerances.ini
new file mode 100644
index 0000000..69ad6eb
--- /dev/null
+++ b/tests/gcode/linuxcnc_g64_default_tolerances.ini
@@ -0,0 +1,3 @@
+[RS274NGC]
+G64_DEFAULT_TOLERANCE = 0.07
+G64_DEFAULT_NAIVETOLERANCE = 0.04
diff --git a/tests/gcode/linuxcnc_g64_default_tolerances.ngc b/tests/gcode/linuxcnc_g64_default_tolerances.ngc
new file mode 100644
index 0000000..d29256b
--- /dev/null
+++ b/tests/gcode/linuxcnc_g64_default_tolerances.ngc
@@ -0,0 +1,4 @@
+G21 G90 G17
+(Source basis: LinuxCNC src/emc/rs274ngc/rs274ngc_pre.cc reads G64_DEFAULT_TOLERANCE and G64_DEFAULT_NAIVETOLERANCE for G64 without P/Q.)
+G64
+M30