diff --git a/usr.bin/diff/diffreg.c b/usr.bin/diff/diffreg.c
--- a/usr.bin/diff/diffreg.c
+++ b/usr.bin/diff/diffreg.c
@@ -369,7 +369,9 @@
 		goto closem;
 	}
 
-	if (diff_format == D_BRIEF && ignore_pats == NULL) {
+	if (diff_format == D_BRIEF && ignore_pats == NULL &&
+	    (flags & (D_FOLDBLANKS|D_IGNOREBLANKS|D_IGNORECASE|D_STRIPCR)) == 0)
+	{
 		rval = D_DIFFER;
 		status |= 1;
 		goto closem;
diff --git a/usr.bin/diff/tests/diff_test.sh b/usr.bin/diff/tests/diff_test.sh
--- a/usr.bin/diff/tests/diff_test.sh
+++ b/usr.bin/diff/tests/diff_test.sh
@@ -9,6 +9,7 @@
 atf_test_case side_by_side
 atf_test_case brief_format
 atf_test_case b230049
+atf_test_case b252515
 atf_test_case Bflag
 atf_test_case Nflag
 atf_test_case tabsize
@@ -65,6 +66,14 @@
 		    b230049_a.in b230049_b.in
 }
 
+b252515_body()
+{
+	printf 'a b\n' > b252515_a.in
+	printf 'a  b\n' > b252515_b.in
+	atf_check -o empty -s eq:0 \
+		diff -qw b252515_a.in b252515_b.in
+}
+
 header_body()
 {
 	export TZ=UTC
@@ -228,6 +237,7 @@
 	atf_add_test_case side_by_side
 	atf_add_test_case brief_format
 	atf_add_test_case b230049
+	atf_add_test_case b252515
 	atf_add_test_case Bflag
 	atf_add_test_case Nflag
 	atf_add_test_case tabsize