2 files changed, 10 insertions, 1 deletions

diff --git a/tools/regression/usr.bin/sed/multitest.t b/tools/regression/usr.bin/sed/multitest.t
index 53c14c56feb9..fefc70b02420 100644
--- a/tools/regression/usr.bin/sed/multitest.t
+++ b/tools/regression/usr.bin/sed/multitest.t
@@ -432,6 +432,15 @@ u2/g' lines1
 	# POSIX does not say that this should work,
 	# but it does for GNU, BSD, and SunOS
 	mark '8.17' ; $SED -e 's/[/]/Q/' lines1
+
+	COMMENT='[ as an s delimiter and its escapes'
+	mark '8.18' ; $SED -e 's[_[X[' lines1
+	# This is a matter of interpretation
+	# POSIX 1003.1, 2004 says "Within the BRE and the replacement,
+	# the BRE delimiter itself can be used as a *literal* character
+	# if it is preceded by a backslash
+	mark '8.19' ; sed 's/l/[/' lines1 | $SED -e 's[\[.[X['
+	mark '8.20' ; sed 's/l/[/' lines1 | $SED -e 's[\[.[X\[['
 }
 
 test_error()
diff --git a/usr.bin/sed/compile.c b/usr.bin/sed/compile.c
index 53e2af76df77..a51a314ae3b1 100644
--- a/usr.bin/sed/compile.c
+++ b/usr.bin/sed/compile.c
@@ -387,7 +387,7 @@ compile_delimited(char *p, char *d)
 		errx(1, "%lu: %s: newline can not be used as a string delimiter",
 				linenum, fname);
 	while (*p) {
-		if (*p == '[') {
+		if (*p == '[' && *p != c) {
 			if ((d = compile_ccl(&p, d)) == NULL)
 				errx(1, "%lu: %s: unbalanced brackets ([])", linenum, fname);
 			continue;