diff --git a/src/languages/gcode.js b/src/languages/gcode.js
index a26b2a7849..405cf0fa9b 100644
--- a/src/languages/gcode.js
+++ b/src/languages/gcode.js
@@ -76,6 +76,10 @@ export default function(hljs) {
       return;
     }
 
+    if (charBeforeMatch === '_') {
+      return;
+    }
+
     response.ignoreMatch();
   }
 
diff --git a/test/markup/gcode/extended.expect.txt b/test/markup/gcode/extended.expect.txt
index 954d2f3a2a..166c830f19 100644
--- a/test/markup/gcode/extended.expect.txt
+++ b/test/markup/gcode/extended.expect.txt
@@ -81,4 +81,6 @@ SET_SKEW XY=<span class="hljs-number">100.0000</span>,<span class="hljs-number">
 SKEW_PROFILE SAVE=<span class="hljs-string">&quot;this name has spaces&quot;</span>
 SAVE_CONFIG
 
+SKEW_PROFILE SAVE=some_ <span class="hljs-title function_">G123</span>
+SKEW_PROFILE SAVE=some_<span class="hljs-title function_">G123</span>
 <span class="hljs-keyword">%</span>
diff --git a/test/markup/gcode/extended.txt b/test/markup/gcode/extended.txt
index dbcf52ed7b..b6b81a107d 100644
--- a/test/markup/gcode/extended.txt
+++ b/test/markup/gcode/extended.txt
@@ -81,4 +81,6 @@ SET_SKEW XY=100.0000,100.0000,70.7107
 SKEW_PROFILE SAVE="this name has spaces"
 SAVE_CONFIG
 
+SKEW_PROFILE SAVE=some_ G123
+SKEW_PROFILE SAVE=some_G123
 %