diff --git a/lisp/llvm-lib/c-compiler-option-sets.el b/lisp/llvm-lib/c-compiler-option-sets.el
index b7133be..a5bfe02 100644
--- a/lisp/llvm-lib/c-compiler-option-sets.el
+++ b/lisp/llvm-lib/c-compiler-option-sets.el
@@ -44,17 +44,17 @@
 
 (cl-defgeneric cos/to-string (config))
 
-(defun cos/edit-compiler-options (optionset current-name)
+(defun cos/edit-compiler-options (prefix optionset current-name)
   (dolist (slot (cddr (eieio-class-slots 'compiler-option-config)))
     (let* ((slot-sym (eieio-slot-descriptor-name slot))
-           (slot-val (and (slot-boundp optionsset slot-sym)
-                          (slot-value optionsset slot-sym))))
+           (slot-val (and (slot-boundp optionset slot-sym)
+                          (slot-value optionset slot-sym))))
       (when slot-val
         (pcase (cl--slot-descriptor-type slot)
           ('list
            (when (or prefix
                      (not (zerop (length slot-val))))
-             (setf (slot-value optionsset slot-sym)
+             (setf (slot-value optionset slot-sym)
                    (read
                     (read-string (format "Edit '%s' for optionset '%s': "
                                          (symbol-name slot-sym)
@@ -63,7 +63,7 @@
           ('string
            (when (or prefix
                      (not (string= slot-val "")))
-             (setf (slot-value optionsset slot-sym)
+             (setf (slot-value optionset slot-sym)
                    (read-string (format "Edit '%s' for optionset '%s': "
                                         (symbol-name slot-sym)
                                         current-name)
diff --git a/lisp/llvm-lib/clang-command.el b/lisp/llvm-lib/clang-command.el
index 64578f3..4be800e 100644
--- a/lisp/llvm-lib/clang-command.el
+++ b/lisp/llvm-lib/clang-command.el
@@ -174,7 +174,7 @@
           (or (and (gethash (buffer-file-name) clang/file-specific-options )
                    "file-specific")
               (gethash target clang/current-target-optionset))))
-    (cos/edit-compiler-options options-config current-name)))
+    (cos/edit-compiler-options prefix options-config current-name)))
 
 (defun clang/clang-options-merge (primary secondary)
   (make-instance