diff --git a/core/src/smoke_gcode_parser.cpp b/core/src/smoke_gcode_parser.cpp
index 422dd79..13eb3c9 100644
--- a/core/src/smoke_gcode_parser.cpp
+++ b/core/src/smoke_gcode_parser.cpp
@@ -644,21 +644,26 @@ int supported_linuxcnc_m_modal_group(int value) {
 }
 
 bool check_linuxcnc_modal_group_conflicts(const std::vector<Word> &word_list, std::string *error) {
-    std::array<bool, 17> g_modes{};
+    std::array<int, 17> g_modes{};
     std::array<bool, 11> m_modes{};
+    g_modes.fill(-1);
     for (const Word &word : word_list) {
         if (word.letter == 'G') {
             const int mode = supported_linuxcnc_g_modal_group(word.value);
             if (mode < 0) {
                 continue;
             }
-            if (g_modes[static_cast<size_t>(mode)]) {
+            const int code = linuxcnc_g_code_number(word.value);
+            const int previous_code = g_modes[static_cast<size_t>(mode)];
+            if (previous_code != -1 && previous_code != 800 && code != 800) {
                 if (error) {
                     *error = "Two G codes used from same modal group";
                 }
                 return false;
             }
-            g_modes[static_cast<size_t>(mode)] = true;
+            if (previous_code == -1 || previous_code == 800) {
+                g_modes[static_cast<size_t>(mode)] = code;
+            }
         } else if (word.letter == 'M') {
             const int mode = supported_linuxcnc_m_modal_group(rounded_value(word.value));
             if (mode < 0) {
diff --git a/core/tests/cnc_sim_api_smoke.cpp b/core/tests/cnc_sim_api_smoke.cpp
index d78e9b8..bc1c5c3 100644
--- a/core/tests/cnc_sim_api_smoke.cpp
+++ b/core/tests/cnc_sim_api_smoke.cpp
@@ -3582,6 +3582,26 @@ int main() {
                                        sizeof(same_modal_group_g_program) - 1) != 0,
                  "expected LinuxCNC to reject two G codes from the same modal group");
 
+    const char g80_before_motion_program[] =
+        "G21 G90\n"
+        "F100\n"
+        "G80 G1 X1\n";
+    events.clear();
+    ok &= expect(cnc_sim_parse_program(sim,
+                                       g80_before_motion_program,
+                                       sizeof(g80_before_motion_program) - 1) == 0,
+                 "expected LinuxCNC to allow G80 before another motion G code");
+
+    const char g80_after_motion_program[] =
+        "G21 G90\n"
+        "F100\n"
+        "G1 G80 X1\n";
+    events.clear();
+    ok &= expect(cnc_sim_parse_program(sim,
+                                       g80_after_motion_program,
+                                       sizeof(g80_after_motion_program) - 1) == 0,
+                 "expected LinuxCNC to allow G80 after another motion G code");
+
     const char same_modal_group_m_program[] =
         "G21 G90\n"
         "M3 M4\n";