diff --git a/src/regexp.c b/src/regexp.c
index b9a111caf1..d84536dafe 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -700,15 +700,6 @@ int re_multiline(regprog_T *prog)
   return prog->regflags & RF_HASNL;
 }
 
-/*
- * Return TRUE if compiled regular expression "prog" looks before the start
- * position (pattern contains "\@<=" or "\@<!").
- */
-int re_lookbehind(regprog_T *prog)
-{
-  return prog->regflags & RF_LOOKBH;
-}
-
 /*
  * Check for an equivalence class name "[=a=]".  "pp" points to the '['.
  * Returns a character representing the class. Zero means that no item was
diff --git a/src/regexp.h b/src/regexp.h
index 8de3ef2288..8d4c921b37 100644
--- a/src/regexp.h
+++ b/src/regexp.h
@@ -2,7 +2,6 @@
 #define NEOVIM_REGEXP_H
 /* regexp.c */
 int re_multiline(regprog_T *prog);
-int re_lookbehind(regprog_T *prog);
 char_u *skip_regexp(char_u *startp, int dirc, int magic, char_u **newp);
 int vim_regcomp_had_eol(void);
 void free_regexp_stuff(void);