diff --git a/src/regexp.c b/src/regexp.c
index 2804f80..369516a 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -361,8 +361,10 @@
 static char_u e_unmatchedpp[] = N_("E53: Unmatched %s%%(");
 static char_u e_unmatchedp[] = N_("E54: Unmatched %s(");
 static char_u e_unmatchedpar[] = N_("E55: Unmatched %s)");
+#ifdef FEAT_SYN_HL
 static char_u e_z_not_allowed[] = N_("E66: \\z( not allowed here");
 static char_u e_z1_not_allowed[] = N_("E67: \\z1 et al. not allowed here");
+#endif
 
 #define NOT_MULTI	0
 #define MULTI_ONE	1