diff --git a/wasm-port/docs/porting-steps-standalone.md b/wasm-port/docs/porting-steps-standalone.md
index ae2c29a..4492279 100644
--- a/wasm-port/docs/porting-steps-standalone.md
+++ b/wasm-port/docs/porting-steps-standalone.md
@@ -365,6 +365,11 @@ Current verified progress:
   current-position parameter visibility for `#5420`, `#5421`, and `#5422`.
   The parameter source basis is LinuxCNC
   `interp_parameter_def.hh` and `interp_namedparams.cc`.
+- `tests/fixtures/gcode_errors/g1_zero_feed.ngc` and
+  `tests/fixtures/canon_errors/g1_zero_feed.expected` pin the negative
+  `G1` zero-feed case. The source basis is LinuxCNC
+  `interp_convert.cc::convert_straight()` and
+  `rs274ngc_return.hh::NCE_CANNOT_DO_G1_WITH_ZERO_FEED_RATE`.
 - This proves the current extracted interpreter slice can parse and execute a
   simple traverse and feed move through a standalone canonical event sink.
 
@@ -667,7 +672,7 @@ traverse path:
 
 1. replace the temporary minimal `convert_g()` implementation with thin
    wrappers around more vendored interpreter conversion code,
-2. add a negative fixture for `G1` without feed rate to start pinning error
-   semantics,
+2. add `_x`/`_y`/`_z` named parameter fixture coverage and align it with
+   `#5420`/`#5421`/`#5422`,
 3. keep all source changes inside `wasm-port/` and leave `../linuxcnc/`
    read-only.
diff --git a/wasm-port/runtime/core/linuxcnc_wrap/linuxcnc_interp_minimal_runtime.cpp b/wasm-port/runtime/core/linuxcnc_wrap/linuxcnc_interp_minimal_runtime.cpp
index 161673f..5f38c7a 100644
--- a/wasm-port/runtime/core/linuxcnc_wrap/linuxcnc_interp_minimal_runtime.cpp
+++ b/wasm-port/runtime/core/linuxcnc_wrap/linuxcnc_interp_minimal_runtime.cpp
@@ -10,6 +10,7 @@
 #include "emc/rs274ngc/rs274ngc_interp.hh"
 #undef private
 
+#include "emc/rs274ngc/rs274ngc_return.hh"
 #include "canon_event_sink.hh"
 
 PythonPlugin *python_plugin = nullptr;
@@ -381,6 +382,13 @@ int Interp::convert_g(block_pointer block, setup_pointer settings)
         SET_FEED_RATE(block->f_number);
     }
 
+    if ((block->motion_to_be == G_1) &&
+        (settings->feed_mode == FEED_MODE::UNITS_PER_MINUTE) &&
+        (settings->feed_rate == 0.0)) {
+        setError("%s", NCE_CANNOT_DO_G1_WITH_ZERO_FEED_RATE);
+        return INTERP_ERROR;
+    }
+
     const bool incremental = settings->distance_mode == DISTANCE_MODE::INCREMENTAL;
     if (block->x_flag) {
         settings->current_x = incremental ? settings->current_x + block->x_number
diff --git a/wasm-port/tests/fixtures/canon_errors/g1_zero_feed.expected b/wasm-port/tests/fixtures/canon_errors/g1_zero_feed.expected
new file mode 100644
index 0000000..2efceb3
--- /dev/null
+++ b/wasm-port/tests/fixtures/canon_errors/g1_zero_feed.expected
@@ -0,0 +1,9 @@
+execute_line_1=5
+error_text=Cannot do g1 with zero feed rate
+setup.current_x=0
+setup.current_y=0
+setup.current_z=0
+setup.parameter_5420=0
+setup.parameter_5421=0
+setup.parameter_5422=0
+absent=canon_event=STRAIGHT_FEED
diff --git a/wasm-port/tests/fixtures/gcode_errors/g1_zero_feed.ngc b/wasm-port/tests/fixtures/gcode_errors/g1_zero_feed.ngc
new file mode 100644
index 0000000..b3e98be
--- /dev/null
+++ b/wasm-port/tests/fixtures/gcode_errors/g1_zero_feed.ngc
@@ -0,0 +1 @@
+G1 X1.0
diff --git a/wasm-port/tests/native/verify_native_probes.sh b/wasm-port/tests/native/verify_native_probes.sh
index b7dda83..14a0e50 100755
--- a/wasm-port/tests/native/verify_native_probes.sh
+++ b/wasm-port/tests/native/verify_native_probes.sh
@@ -5,6 +5,8 @@ ROOT_DIR="$(cd "$(dirname "$0")/../.." && pwd)"
 BUILD_DIR="$ROOT_DIR/build/native"
 GCODE_FIXTURE_DIR="$ROOT_DIR/tests/fixtures/gcode"
 CANON_FIXTURE_DIR="$ROOT_DIR/tests/fixtures/canon"
+GCODE_ERROR_FIXTURE_DIR="$ROOT_DIR/tests/fixtures/gcode_errors"
+CANON_ERROR_FIXTURE_DIR="$ROOT_DIR/tests/fixtures/canon_errors"
 
 "$ROOT_DIR/tools/build_native_probes.sh"
 
@@ -77,4 +79,34 @@ for fixture in "$GCODE_FIXTURE_DIR"/*.ngc; do
   check_fixture_output "$fixture" "$expected" "$stdout_file"
 done
 
+for fixture in "$GCODE_ERROR_FIXTURE_DIR"/*.ngc; do
+  name="$(basename "$fixture" .ngc)"
+  expected="$CANON_ERROR_FIXTURE_DIR/$name.expected"
+  if [[ ! -f "$expected" ]]; then
+    echo "missing expected error fixture: $expected" >&2
+    exit 1
+  fi
+
+  stdout_file="$BUILD_DIR/linuxcnc_interp_minimal_harness.$name.stdout.log"
+  stderr_file="$BUILD_DIR/linuxcnc_interp_minimal_harness.$name.stderr.log"
+  "$BUILD_DIR/linuxcnc_interp_minimal_harness" "$fixture" \
+    >"$stdout_file" \
+    2>"$stderr_file"
+
+  while IFS= read -r expected_line; do
+    [[ -z "$expected_line" ]] && continue
+    if [[ "$expected_line" == absent=* ]]; then
+      forbidden="${expected_line#absent=}"
+      if grep -Fq "$forbidden" "$stdout_file"; then
+        echo "unexpected output in $stdout_file: $forbidden" >&2
+        exit 1
+      fi
+    elif [[ "$expected_line" == error_text=* ]]; then
+      grep -Fq "${expected_line#error_text=}" "$stderr_file"
+    else
+      grep -Fq "$expected_line" "$stdout_file"
+    fi
+  done < "$expected"
+done
+
 echo "native probe validation complete"