diff --git a/src/cmp/cmpffi.lsp b/src/cmp/cmpffi.lsp
index fd4845201..7db92f033 100644
--- a/src/cmp/cmpffi.lsp
+++ b/src/cmp/cmpffi.lsp
@@ -343,7 +343,8 @@
 	  ((>= ndx (length c-expression)))
 	(let ((c (char c-expression ndx)))
 	  (when (eq c #\;)
-	    (setf c-expression (subseq c-expression (1+ c))))
+	    (setf c-expression (subseq c-expression (1+ ndx)))
+	    (return))
 	  (unless (alphanumericp c)
 	    (setf args-to-be-saved nil)
 	    (return))