diff --git a/test-all-native.sh b/test-all-native.sh
index 17d1a5d..bb88c59 100755
--- a/test-all-native.sh
+++ b/test-all-native.sh
@@ -564,6 +564,7 @@ grep -F 'read_n_number()' test-linuxcnc-source-link.sh >/dev/null
 grep -F 'tests/gcode/linuxcnc_fractional_linenumbers.ngc' test-linuxcnc-source-link.sh >/dev/null
 grep -F 'tests/gcode/linuxcnc_extended_linenumbers.ngc' test-linuxcnc-source-link.sh >/dev/null
 grep -F 'tests/gcode/linuxcnc_close_and_downcase_words.ngc' test-linuxcnc-source-link.sh >/dev/null
+grep -F 'tests/gcode/linuxcnc_percent_file_ignores_trailing.ngc' test-linuxcnc-source-link.sh >/dev/null
 
 for script in \
     test-native.sh \
diff --git a/test-linuxcnc-source-link.sh b/test-linuxcnc-source-link.sh
index a7c0108..2823f9c 100755
--- a/test-linuxcnc-source-link.sh
+++ b/test-linuxcnc-source-link.sh
@@ -1501,6 +1501,13 @@ CNC_SIM_RS274_VAR="$var_file" \
 CNC_SIM_RS274_VAR="$var_file" \
     "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_close_and_downcase_words.ngc \
     >"$output_dir/cnc_sim_linuxcnc_source_close_and_downcase_words.json"
+# Source basis: LinuxCNC src/emc/rs274ngc/rs274ngc_pre.cc open() enables
+# percent-file mode when the first nonblank line is '%'; read_text() in
+# src/emc/rs274ngc/interp_read.cc returns INTERP_ENDFILE at the matching '%',
+# so later lines are ignored.
+CNC_SIM_RS274_FILE_MODE=1 CNC_SIM_RS274_VAR="$var_file" \
+    "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_percent_file_ignores_trailing.ngc \
+    >"$output_dir/cnc_sim_linuxcnc_source_percent_file_ignores_trailing.json"
 
 CNC_SIM_RS274_SOURCE_OUTPUT_DIR="$output_dir" python3 - <<'PY'
 import json
@@ -1572,6 +1579,18 @@ if not any(
 ):
     raise SystemExit("missing source-linked close_and_downcase mixed-case spaced-word move")
 
+percent_file = load("cnc_sim_linuxcnc_source_percent_file_ignores_trailing.json")
+percent_file_feeds = [
+    (event["line"], event["end"]["x"])
+    for event in percent_file
+    if event["type"] == "linear-feed"
+]
+if percent_file_feeds != [(4, 1)]:
+    raise SystemExit(
+        "unexpected source-linked percent-file feed sequence: "
+        f"{percent_file_feeds!r}"
+    )
+
 block_delete_off = load("cnc_sim_linuxcnc_source_block_delete_off.json")
 if not any(
     event["type"] == "linear-feed" and event["line"] == 2 and event["end"]["x"] == 5
@@ -3461,3 +3480,4 @@ echo "dumped $output_dir/cnc_sim_linuxcnc_source_g62_xz_nurbs.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_source_fractional_linenumbers.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_source_extended_linenumbers.json"
 echo "dumped $output_dir/cnc_sim_linuxcnc_source_close_and_downcase_words.json"
+echo "dumped $output_dir/cnc_sim_linuxcnc_source_percent_file_ignores_trailing.json"
diff --git a/tests/gcode/linuxcnc_percent_file_ignores_trailing.ngc b/tests/gcode/linuxcnc_percent_file_ignores_trailing.ngc
new file mode 100644
index 0000000..aadece0
--- /dev/null
+++ b/tests/gcode/linuxcnc_percent_file_ignores_trailing.ngc
@@ -0,0 +1,6 @@
+%
+G21 G90
+F100
+G1 X1
+%
+G1 X99