diff --git a/config.h b/config.h
index 84eff6f..88109d3 100644
--- a/config.h
+++ b/config.h
@@ -28,6 +28,10 @@
 #ifndef config_h
 #define config_h
 
+// Allows GRBL to tranck and report gcode line numbers.  Enabling this means that the planning buffer
+// goes from 18 or 16 to make room for the additional line number data in the plan_block_t struct
+#define USE_LINE_NUMBERS
+
 // Default settings. Used when resetting EEPROM. Change to desired name in defaults.h
 #define DEFAULTS_SHERLINE_5400
 
diff --git a/gcode.c b/gcode.c
index 3306abb..450f9af 100644
--- a/gcode.c
+++ b/gcode.c
@@ -101,6 +101,7 @@ uint8_t gc_execute_line(char *line)
   float target[N_AXIS];
   clear_vector(target); // XYZ(ABC) axes parameters.
 
+  uint32_t line_number = 0;
   gc.arc_radius = 0;
   clear_vector(gc.arc_offset); // IJK Arc offsets are incremental. Value of zero indicates no change.
 
@@ -215,7 +216,7 @@ uint8_t gc_execute_line(char *line)
   char_counter = 0;
   while(next_statement(&letter, &value, line, &char_counter)) {
     switch(letter) {
-      case 'G': case 'M': case 'N': break; // Ignore command statements and line numbers
+      case 'G': case 'M': break; // Ignore command statements and line numbers
       case 'F': 
         if (value <= 0) { FAIL(STATUS_INVALID_STATEMENT); } // Must be greater than zero
         if (gc.inverse_feed_rate_mode) {
@@ -226,6 +227,7 @@ uint8_t gc_execute_line(char *line)
         break;
       case 'I': case 'J': case 'K': gc.arc_offset[letter-'I'] = to_millimeters(value); break;
       case 'L': l = trunc(value); break;
+      case 'N': line_number = trunc(value); break;
       case 'P': p = value; break;                    
       case 'R': gc.arc_radius = to_millimeters(value); break;
       case 'S': 
@@ -329,7 +331,7 @@ uint8_t gc_execute_line(char *line)
             target[idx] = gc.position[idx];
           }
         }
-        mc_line(target, -1.0, false);
+        mc_line(target, -1.0, false, line_number);
       }
       // Retreive G28/30 go-home position data (in machine coordinates) from EEPROM
       float coord_data[N_AXIS];
@@ -338,7 +340,7 @@ uint8_t gc_execute_line(char *line)
       } else {
         if (!settings_read_coord_data(SETTING_INDEX_G30,coord_data)) { return(STATUS_SETTING_READ_FAIL); }
       }
-      mc_line(coord_data, -1.0, false); 
+      mc_line(coord_data, -1.0, false, line_number); 
       memcpy(gc.position, coord_data, sizeof(coord_data)); // gc.position[] = coord_data[];
       axis_words = 0; // Axis words used. Lock out from motion modes by clearing flags.
       break;
@@ -409,7 +411,7 @@ uint8_t gc_execute_line(char *line)
         break;
       case MOTION_MODE_SEEK:
         if (!axis_words) { FAIL(STATUS_INVALID_STATEMENT);} 
-        else { mc_line(target, -1.0, false); }
+        else { mc_line(target, -1.0, false, line_number); }
         break;
       case MOTION_MODE_LINEAR:
         // TODO: Inverse time requires F-word with each statement. Need to do a check. Also need
@@ -417,7 +419,7 @@ uint8_t gc_execute_line(char *line)
         // and after an inverse time move and then check for non-zero feed rate each time. This
         // should be efficient and effective.
         if (!axis_words) { FAIL(STATUS_INVALID_STATEMENT);} 
-        else { mc_line(target, (gc.inverse_feed_rate_mode) ? inverse_feed_rate : gc.feed_rate, gc.inverse_feed_rate_mode); }
+        else { mc_line(target, (gc.inverse_feed_rate_mode) ? inverse_feed_rate : gc.feed_rate, gc.inverse_feed_rate_mode, line_number); }
         break;
       case MOTION_MODE_CW_ARC: case MOTION_MODE_CCW_ARC:
         // Check if at least one of the axes of the selected plane has been specified. If in center 
@@ -441,7 +443,7 @@ uint8_t gc_execute_line(char *line)
           // Trace the arc
           mc_arc(gc.position, target, gc.arc_offset, gc.plane_axis_0, gc.plane_axis_1, gc.plane_axis_2,
             (gc.inverse_feed_rate_mode) ? inverse_feed_rate : gc.feed_rate, gc.inverse_feed_rate_mode,
-            gc.arc_radius, isclockwise);
+            gc.arc_radius, isclockwise, line_number);
         }            
         break;
     }
diff --git a/limits.c b/limits.c
index 1660ec4..10f0311 100644
--- a/limits.c
+++ b/limits.c
@@ -83,13 +83,13 @@ void limits_disable()
     // moves in the planner and serial buffers are all cleared and newly sent blocks will be 
     // locked out until a homing cycle or a kill lock command. Allows the user to disable the hard
     // limit setting if their limits are constantly triggering after a reset and move their axes.
-    if (sys.state != STATE_ALARM) {
+    if (sys.state != STATE_ALARM) { 
       if (bit_isfalse(sys.execute,EXEC_ALARM)) {
-        mc_reset(); // Initiate system kill.
-        sys.execute |= EXEC_CRIT_EVENT; // Indicate hard limit critical event
+          mc_reset(); // Initiate system kill.
+          sys.execute |= EXEC_CRIT_EVENT; // Indicate hard limit critical event
+        }
       }
     }  
-  }
 #else // OPTIONAL: Software debounce limit pin routine.
   // Upon limit pin change, enable watchdog timer to create a short delay. 
   ISR(LIMIT_INT_vect) { if (!(WDTCSR & (1<<WDIE))) { WDTCSR |= (1<<WDIE); } }
@@ -102,12 +102,12 @@ void limits_disable()
         // Check limit pin state. 
         if (bit_istrue(settings.flags,BITFLAG_INVERT_LIMIT_PINS)) { bits ^= LIMIT_MASK; }
         if (bits & LIMIT_MASK) {
-          mc_reset(); // Initiate system kill.
-          sys.execute |= EXEC_CRIT_EVENT; // Indicate hard limit critical event
-        }
+        mc_reset(); // Initiate system kill.
+        sys.execute |= EXEC_CRIT_EVENT; // Indicate hard limit critical event
       }
     }  
   }
+  }
 #endif
 
 
@@ -120,14 +120,14 @@ void limits_disable()
 void limits_go_home(uint8_t cycle_mask) 
 {
   if (sys.abort) { return; } // Block if system reset has been issued.
-  
+
   // Initialize homing in search mode to quickly engage the specified cycle_mask limit switches.
   bool approach = true;
   float homing_rate = settings.homing_seek_rate;
   uint8_t invert_pin, idx;
   uint8_t n_cycle = (2*N_HOMING_LOCATE_CYCLE+1);
   float target[N_AXIS];
-
+  
   // Determine travel distance to the furthest homing switch based on user max travel settings.
   // NOTE: settings.max_travel[] is stored as a negative value.
   float max_travel = settings.max_travel[X_AXIS];
@@ -142,58 +142,58 @@ void limits_go_home(uint8_t cycle_mask)
     if (bit_isfalse(settings.flags,BITFLAG_INVERT_LIMIT_PINS)) { invert_pin = approach; }
     else { invert_pin = !approach; }
 
-    // Set target location and rate for active axes.
-    uint8_t n_active_axis = 0;
+  // Set target location and rate for active axes.
+  uint8_t n_active_axis = 0;
     for (idx=0; idx<N_AXIS; idx++) {
       if (bit_istrue(cycle_mask,bit(idx))) { 
-        n_active_axis++;
+      n_active_axis++;
         if (!approach) { target[idx] = -max_travel; }
         else { target[idx] = max_travel; }
-       } else {
+     } else {
         target[idx] = 0.0;
-      }
-    }      
-    if (bit_istrue(settings.homing_dir_mask,(1<<X_DIRECTION_BIT))) { target[X_AXIS] = -target[X_AXIS]; }
-    if (bit_istrue(settings.homing_dir_mask,(1<<Y_DIRECTION_BIT))) { target[Y_AXIS] = -target[Y_AXIS]; }
-    if (bit_istrue(settings.homing_dir_mask,(1<<Z_DIRECTION_BIT))) { target[Z_AXIS] = -target[Z_AXIS]; }
+    }
+  }      
+  if (bit_istrue(settings.homing_dir_mask,(1<<X_DIRECTION_BIT))) { target[X_AXIS] = -target[X_AXIS]; }
+  if (bit_istrue(settings.homing_dir_mask,(1<<Y_DIRECTION_BIT))) { target[Y_AXIS] = -target[Y_AXIS]; }
+  if (bit_istrue(settings.homing_dir_mask,(1<<Z_DIRECTION_BIT))) { target[Z_AXIS] = -target[Z_AXIS]; }
   
-    homing_rate *= sqrt(n_active_axis); // [sqrt(N_AXIS)] Adjust so individual axes all move at homing rate.
+  homing_rate *= sqrt(n_active_axis); // [sqrt(N_AXIS)] Adjust so individual axes all move at homing rate.
 
     // Reset homing axis locks based on cycle mask. 
-    uint8_t axislock = 0;
-    if (bit_istrue(cycle_mask,bit(X_AXIS))) { axislock |= (1<<X_STEP_BIT); }
-    if (bit_istrue(cycle_mask,bit(Y_AXIS))) { axislock |= (1<<Y_STEP_BIT); }
-    if (bit_istrue(cycle_mask,bit(Z_AXIS))) { axislock |= (1<<Z_STEP_BIT); }
-    sys.homing_axis_lock = axislock;
+  uint8_t axislock = 0;
+  if (bit_istrue(cycle_mask,bit(X_AXIS))) { axislock |= (1<<X_STEP_BIT); }
+  if (bit_istrue(cycle_mask,bit(Y_AXIS))) { axislock |= (1<<Y_STEP_BIT); }
+  if (bit_istrue(cycle_mask,bit(Z_AXIS))) { axislock |= (1<<Z_STEP_BIT); }
+  sys.homing_axis_lock = axislock;
   
-    // Perform homing cycle. Planner buffer should be empty, as required to initiate the homing cycle.
-    uint8_t limit_state;
-    plan_buffer_line(target, homing_rate, false); // Bypass mc_line(). Directly plan homing motion.
+  // Perform homing cycle. Planner buffer should be empty, as required to initiate the homing cycle.
+  uint8_t limit_state;
+  plan_buffer_line(target, homing_rate, false, HOMING_CYCLE_LINE_NUMBER); // Bypass mc_line(). Directly plan homing motion.
     st_prep_buffer(); // Prep and fill segment buffer from newly planned block.
-    st_wake_up(); // Initiate motion
-    do {
-      // Check limit state. Lock out cycle axes when they change.
-      limit_state = LIMIT_PIN;
-      if (invert_pin) { limit_state ^= LIMIT_MASK; }
-      if (axislock & (1<<X_STEP_BIT)) {
-        if (limit_state & (1<<X_LIMIT_BIT)) { axislock &= ~(1<<X_STEP_BIT); }
-      }
-      if (axislock & (1<<Y_STEP_BIT)) {
-        if (limit_state & (1<<Y_LIMIT_BIT)) { axislock &= ~(1<<Y_STEP_BIT); }
-      }
-      if (axislock & (1<<Z_STEP_BIT)) {
-        if (limit_state & (1<<Z_LIMIT_BIT)) { axislock &= ~(1<<Z_STEP_BIT); }
-      }
-      sys.homing_axis_lock = axislock;
+  st_wake_up(); // Initiate motion
+  do {
+    // Check limit state. Lock out cycle axes when they change.
+    limit_state = LIMIT_PIN;
+    if (invert_pin) { limit_state ^= LIMIT_MASK; }
+    if (axislock & (1<<X_STEP_BIT)) {
+      if (limit_state & (1<<X_LIMIT_BIT)) { axislock &= ~(1<<X_STEP_BIT); }
+    }
+    if (axislock & (1<<Y_STEP_BIT)) {
+      if (limit_state & (1<<Y_LIMIT_BIT)) { axislock &= ~(1<<Y_STEP_BIT); }
+    }
+    if (axislock & (1<<Z_STEP_BIT)) {
+      if (limit_state & (1<<Z_LIMIT_BIT)) { axislock &= ~(1<<Z_STEP_BIT); }
+    }
+    sys.homing_axis_lock = axislock;
       st_prep_buffer(); // Check and prep segment buffer. NOTE: Should take no longer than 200us.
       // Check only for user reset. No time to run protocol_execute_runtime() in this loop.
       if (sys.execute & EXEC_RESET) { protocol_execute_runtime(); return; }
-    } while (STEP_MASK & axislock);
+  } while (STEP_MASK & axislock);
     
     st_reset(); // Immediately force kill steppers and reset step segment buffer.
     plan_reset(); // Reset planner buffer. Zero planner positions. Ensure homing motion is cleared.
 
-    delay_ms(settings.homing_debounce_delay); // Delay to allow transient dynamics to dissipate.  
+  delay_ms(settings.homing_debounce_delay); // Delay to allow transient dynamics to dissipate.
 
     // Reverse direction and reset homing rate for locate cycle(s).
     homing_rate = settings.homing_feed_rate;
@@ -225,7 +225,7 @@ void limits_go_home(uint8_t cycle_mask)
     }
   }
   plan_sync_position(); // Sync planner position to current machine position for pull-off move.
-  plan_buffer_line(target, settings.homing_seek_rate, false); // Bypass mc_line(). Directly plan motion.
+  plan_buffer_line(target, settings.homing_seek_rate, false, HOMING_CYCLE_LINE_NUMBER); // Bypass mc_line(). Directly plan motion.
 
   // Initiate pull-off using main motion control routines. 
   // TODO : Clean up state routines so that this motion still shows homing state.
diff --git a/motion_control.c b/motion_control.c
index f9b1c7b..36caaa7 100644
--- a/motion_control.c
+++ b/motion_control.c
@@ -39,7 +39,7 @@
 // segments, must pass through this routine before being passed to the planner. The seperation of
 // mc_line and plan_buffer_line is done primarily to place non-planner-type functions from being
 // in the planner and to let backlash compensation or canned cycle integration simple and direct.
-void mc_line(float *target, float feed_rate, uint8_t invert_feed_rate)
+void mc_line(float *target, float feed_rate, uint8_t invert_feed_rate, uint32_t line_number)
 {
   // If enabled, check for soft limit violations. Placed here all line motions are picked up
   // from everywhere in Grbl.
@@ -71,7 +71,7 @@ void mc_line(float *target, float feed_rate, uint8_t invert_feed_rate)
     else { break; }
   } while (1);
 
-  plan_buffer_line(target, feed_rate, invert_feed_rate);
+  plan_buffer_line(target, feed_rate, invert_feed_rate, line_number);
 
   // If idle, indicate to the system there is now a planned block in the buffer ready to cycle 
   // start. Otherwise ignore and continue on.
@@ -87,7 +87,7 @@ void mc_line(float *target, float feed_rate, uint8_t invert_feed_rate)
 // of each segment is configured in settings.arc_tolerance, which is defined to be the maximum normal
 // distance from segment to the circle when the end points both lie on the circle.
 void mc_arc(float *position, float *target, float *offset, uint8_t axis_0, uint8_t axis_1, 
-  uint8_t axis_linear, float feed_rate, uint8_t invert_feed_rate, float radius, uint8_t isclockwise)
+  uint8_t axis_linear, float feed_rate, uint8_t invert_feed_rate, float radius, uint8_t isclockwise, uint32_t line_number)
 {      
   float center_axis0 = position[axis_0] + offset[axis_0];
   float center_axis1 = position[axis_1] + offset[axis_1];
@@ -183,14 +183,14 @@ void mc_arc(float *position, float *target, float *offset, uint8_t axis_0, uint8
       arc_target[axis_0] = center_axis0 + r_axis0;
       arc_target[axis_1] = center_axis1 + r_axis1;
       arc_target[axis_linear] += linear_per_segment;
-      mc_line(arc_target, feed_rate, invert_feed_rate);
+      mc_line(arc_target, feed_rate, invert_feed_rate, line_number);
       
       // Bail mid-circle on system abort. Runtime command check already performed by mc_line.
       if (sys.abort) { return; }
     }
   }
   // Ensure last segment arrives at target location.
-  mc_line(target, feed_rate, invert_feed_rate);
+  mc_line(target, feed_rate, invert_feed_rate, line_number);
 }
 
 
@@ -228,16 +228,16 @@ void mc_homing_cycle()
   #ifdef HOMING_CYCLE_2
     limits_go_home(HOMING_CYCLE_2);  // Homing cycle 2
   #endif
-  
+    
   protocol_execute_runtime(); // Check for reset and set system abort.
   if (sys.abort) { return; } // Did not complete. Alarm state set by mc_alarm.
 
   // Homing cycle complete! Setup system for normal operation.
   // -------------------------------------------------------------------------------------
-  
+
   // Gcode parser position was circumvented by the limits_go_home() routine, so sync position now.
   gc_sync_position();
-    
+  
   // Set idle state after homing completes and before returning to main program.  
   sys.state = STATE_IDLE;
   st_go_idle(); // Set idle state after homing completes
diff --git a/motion_control.h b/motion_control.h
index 33acf19..a38e9f2 100644
--- a/motion_control.h
+++ b/motion_control.h
@@ -22,18 +22,19 @@
 #ifndef motion_control_h
 #define motion_control_h
 
+#define HOMING_CYCLE_LINE_NUMBER 1000000000
 
 // Execute linear motion in absolute millimeter coordinates. Feed rate given in millimeters/second
 // unless invert_feed_rate is true. Then the feed_rate means that the motion should be completed in
 // (1 minute)/feed_rate time.
-void mc_line(float *target, float feed_rate, uint8_t invert_feed_rate);
+void mc_line(float *target, float feed_rate, uint8_t invert_feed_rate, uint32_t line_number);
 
 // Execute an arc in offset mode format. position == current xyz, target == target xyz, 
 // offset == offset from current xyz, axis_XXX defines circle plane in tool space, axis_linear is
 // the direction of helical travel, radius == circle radius, isclockwise boolean. Used
 // for vector transformation direction.
 void mc_arc(float *position, float *target, float *offset, uint8_t axis_0, uint8_t axis_1,
-  uint8_t axis_linear, float feed_rate, uint8_t invert_feed_rate, float radius, uint8_t isclockwise);
+  uint8_t axis_linear, float feed_rate, uint8_t invert_feed_rate, float radius, uint8_t isclockwise, uint32_t line_number);
   
 // Dwell for a specific number of seconds
 void mc_dwell(float seconds);
diff --git a/planner.c b/planner.c
index 2eb346b..e7a7c57 100644
--- a/planner.c
+++ b/planner.c
@@ -259,7 +259,7 @@ uint8_t plan_check_full_buffer()
    is used in three ways: as a normal feed rate if invert_feed_rate is false, as inverse time if
    invert_feed_rate is true, or as seek/rapids rate if the feed_rate value is negative (and
    invert_feed_rate always false). */
-void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate) 
+void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate, uint32_t line_number) 
 {
   // Prepare and initialize new block
   plan_block_t *block = &block_buffer[block_buffer_head];
@@ -267,7 +267,9 @@ void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate)
   block->millimeters = 0;
   block->direction_bits = 0;
   block->acceleration = SOME_LARGE_VALUE; // Scaled down to maximum acceleration later
-
+#ifdef USE_LINE_NUMBERS
+  block->line_number = line_number;
+#endif
   // Compute and store initial move distance data.
   // TODO: After this for-loop, we don't touch the stepper algorithm data. Might be a good idea
   // to try to keep these types of things completely separate from the planner for portability.
diff --git a/planner.h b/planner.h
index 535291e..29b571b 100644
--- a/planner.h
+++ b/planner.h
@@ -26,7 +26,11 @@
 
 // The number of linear motions that can be in the plan at any give time
 #ifndef BLOCK_BUFFER_SIZE
-  #define BLOCK_BUFFER_SIZE 18
+  #ifdef USE_LINE_NUMBERS
+    #define BLOCK_BUFFER_SIZE 16
+  #else
+    #define BLOCK_BUFFER_SIZE 18
+  #endif
 #endif
 
 // This struct stores a linear movement of a g-code block motion with its critical "nominal" values
@@ -47,6 +51,9 @@ typedef struct {
   float acceleration;            // Axis-limit adjusted line acceleration in (mm/min^2)
   float millimeters;             // The remaining distance for this block to be executed in (mm)
   // uint8_t max_override;       // Maximum override value based on axis speed limits
+#ifdef USE_LINE_NUMBERS
+  uint32_t line_number;
+#endif
 } plan_block_t;
 
       
@@ -56,7 +63,7 @@ void plan_reset();
 // Add a new linear movement to the buffer. target[N_AXIS] is the signed, absolute target position 
 // in millimeters. Feed rate specifies the speed of the motion. If feed rate is inverted, the feed
 // rate is taken to mean "frequency" and would complete the operation in 1/feed_rate minutes.
-void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate);
+void plan_buffer_line(float *target, float feed_rate, uint8_t invert_feed_rate, uint32_t line_number);
 
 // Called when the current block is no longer needed. Discards the block and makes the memory
 // availible for new blocks.
diff --git a/report.c b/report.c
index 5416651..e17b6a9 100644
--- a/report.c
+++ b/report.c
@@ -32,6 +32,7 @@
 #include "settings.h"
 #include "gcode.h"
 #include "coolant_control.h"
+#include "planner.h"
 #include "spindle_control.h"
 
 
@@ -261,9 +262,9 @@ void report_gcode_modes()
   }
 
   switch (gc.spindle_direction) {
-    case SPINDLE_ENABLE_CW  : printPgmString(PSTR(" M3")); break;
-    case SPINDLE_ENABLE_CCW  : printPgmString(PSTR(" M4")); break;
-    case SPINDLE_DISABLE : printPgmString(PSTR(" M5")); break;
+    case 1 : printPgmString(PSTR(" M3")); break;
+    case -1 : printPgmString(PSTR(" M4")); break;
+    case 0 : printPgmString(PSTR(" M5")); break;
   }
   
   switch (gc.coolant_mode) {
@@ -350,5 +351,17 @@ void report_realtime_status()
     if (i < (N_AXIS-1)) { printPgmString(PSTR(",")); }
   }
     
+#ifdef USE_LINE_NUMBERS
+  // Report current line number
+  printPgmString(PSTR(","));
+  printPgmString(PSTR("Ln:")); 
+  uint32_t ln=0;
+  plan_block_t * pb = plan_get_current_block();
+  if(pb != NULL) {
+    ln = pb->line_number;
+  } 
+  printInteger(ln);
+#endif
+    
   printPgmString(PSTR(">\r\n"));
 }