diff --git a/src/index.js b/src/index.js
index 5e7cb46..45a8b9f 100644
--- a/src/index.js
+++ b/src/index.js
@@ -126,10 +126,15 @@ const parseLine = (() => {
                 continue;
             }
 
+            let value = Number(argument);
+            if (Number.isNaN(value)) {
+                value = argument;
+            }
+
             if (options.flatten) {
-                result.words.push(`${letter}${argument}`);
+                result.words.push(letter + value);
             } else {
-                result.words.push([letter, Number(argument)]);
+                result.words.push([letter, value]);
             }
         }
 
diff --git a/test/index.js b/test/index.js
index de76403..9cdcf31 100644
--- a/test/index.js
+++ b/test/index.js
@@ -152,11 +152,11 @@ describe('gcode-parser', () => {
                 '$H',
                 'F1000',
                 '(*** LAYER: 0 ***)',
-                'T5 M6',
+                'T5 M06',
                 'S200',
                 '(* SHAPE Nr: 0 *)',
                 'G0 X 180.327 Y 137.080',
-                'M3'
+                'M03'
             ].join('\n');
             const expectedResults = [
                 '',