diff --git a/libc/newhdrgen/header.py b/libc/newhdrgen/header.py
index 1c227715991c9a..ee28ada4f557c0 100644
--- a/libc/newhdrgen/header.py
+++ b/libc/newhdrgen/header.py
@@ -57,9 +57,33 @@ def __str__(self):
 
         content.append("\n__BEGIN_C_DECLS\n")
 
+        current_guard = None
         for function in self.functions:
-            content.append(str(function) + "__NOEXCEPT")
-            content.append("")
+            if function.guard == None:
+                content.append(str(function) + "__NOEXCEPT")
+                content.append("")
+            else:
+                if current_guard == None:
+                    current_guard = function.guard
+                    content.append(f"#ifdef {current_guard}")
+                    content.append(str(function) + "__NOEXCEPT")
+                    content.append("")
+                elif current_guard == function.guard:
+                    content.append(str(function) + "__NOEXCEPT")
+                    content.append("")
+                else:
+                    content.pop()
+                    content.append(f"#endif // {current_guard}")
+                    content.append("")
+                    current_guard = function.guard
+                    content.append(f"#ifdef {current_guard}")
+                    content.append(str(function) + "__NOEXCEPT")
+                    content.append("")
+        if current_guard != None:
+            content.pop()
+            content.append(f"#endif // {current_guard}")
+            content.append("")      
+
         for object in self.objects:
             content.append(str(object))
         if self.objects:
@@ -67,4 +91,4 @@ def __str__(self):
         else:
             content.append("__END_C_DECLS")
 
-        return "\n".join(content)
+        return "\n".join(content)
\ No newline at end of file