diff --git a/src/regexp_bt.c b/src/regexp_bt.c
index 1a677d1..313451c 100644
--- a/src/regexp_bt.c
+++ b/src/regexp_bt.c
@@ -2158,7 +2158,7 @@
 			      }
 		}
 		if (lop == END)
-		    EMSG2_RET_NULL(_("E59: invalid character after %s@"),
+		    EMSG2_RET_NULL(_(e_invalid_character_after_str_at),
 						      reg_magic == MAGIC_ALL);
 		// Look behind must match with behind_pos.
 		if (lop == BEHIND || lop == NOBEHIND)
@@ -2199,7 +2199,7 @@
 	    else
 	    {
 		if (num_complex_braces >= 10)
-		    EMSG2_RET_NULL(_("E60: Too many complex %s{...}s"),
+		    EMSG2_RET_NULL(_(e_too_many_complex_str_curly),
 						      reg_magic == MAGIC_ALL);
 		reginsert(BRACE_COMPLEX + num_complex_braces, ret);
 		regoptail(ret, regnode(BACK));
@@ -2369,7 +2369,7 @@
     {
 	// Make a ZOPEN node.
 	if (regnzpar >= NSUBEXP)
-	    EMSG_RET_NULL(_("E50: Too many \\z("));
+	    EMSG_RET_NULL(_(e_too_many_z));
 	parno = regnzpar;
 	regnzpar++;
 	ret = regnode(ZOPEN + parno);
@@ -2380,7 +2380,7 @@
     {
 	// Make a MOPEN node.
 	if (regnpar >= NSUBEXP)
-	    EMSG2_RET_NULL(_("E51: Too many %s("), reg_magic == MAGIC_ALL);
+	    EMSG2_RET_NULL(_(e_too_many_str_open), reg_magic == MAGIC_ALL);
 	parno = regnpar;
 	++regnpar;
 	ret = regnode(MOPEN + parno);
@@ -2437,18 +2437,18 @@
     {
 #ifdef FEAT_SYN_HL
 	if (paren == REG_ZPAREN)
-	    EMSG_RET_NULL(_("E52: Unmatched \\z("));
+	    EMSG_RET_NULL(_(e_unmatched_z));
 	else
 #endif
 	    if (paren == REG_NPAREN)
-	    EMSG2_RET_NULL(_(e_unmatchedpp), reg_magic == MAGIC_ALL);
+	    EMSG2_RET_NULL(_(e_unmatched_str_percent_open), reg_magic == MAGIC_ALL);
 	else
-	    EMSG2_RET_NULL(_(e_unmatchedp), reg_magic == MAGIC_ALL);
+	    EMSG2_RET_NULL(_(e_unmatched_str_open), reg_magic == MAGIC_ALL);
     }
     else if (paren == REG_NOPAREN && peekchr() != NUL)
     {
 	if (curchr == Magic(')'))
-	    EMSG2_RET_NULL(_(e_unmatchedpar), reg_magic == MAGIC_ALL);
+	    EMSG2_RET_NULL(_(e_unmatched_str_close), reg_magic == MAGIC_ALL);
 	else
 	    EMSG_RET_NULL(_(e_trailing));	// "Can't happen".
 	// NOTREACHED