diff --git a/.gitignore b/.gitignore
index 03c03be5..3af8e207 100644
--- a/.gitignore
+++ b/.gitignore
@@ -58,6 +58,7 @@
 /src/bulkstat_null_ocount
 /src/bulkstat_unlink_test
 /src/bulkstat_unlink_test_modified
+/src/chprojid_fail
 /src/cloner
 /src/dbtest
 /src/devzero
diff --git a/src/Makefile b/src/Makefile
index 38ee6718..3d729a34 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -29,7 +29,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
 	attr-list-by-handle-cursor-test listxattr dio-interleaved t_dir_type \
 	dio-invalidate-cache stat_test t_encrypted_d_revalidate \
 	attr_replace_test swapon mkswap t_attr_corruption t_open_tmpfiles \
-	fscrypt-crypt-util bulkstat_null_ocount splice-test
+	fscrypt-crypt-util bulkstat_null_ocount splice-test chprojid_fail
 
 SUBDIRS = log-writes perf
 
diff --git a/src/chprojid_fail.c b/src/chprojid_fail.c
new file mode 100644
index 00000000..8c5b5fee
--- /dev/null
+++ b/src/chprojid_fail.c
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2021 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ *
+ * Regression test for failing to undo delalloc quota reservations when
+ * changing project id and we fail some other FSSETXATTR validation.
+ */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <linux/fs.h>
+
+static char zerobuf[65536];
+
+int
+main(
+	int		argc,
+	char		*argv[])
+{
+	struct fsxattr	fa;
+	ssize_t		sz;
+	int		fd, ret;
+
+	if (argc < 2) {
+		printf("Usage: %s filename\n", argv[0]);
+		return 1;
+	}
+
+	fd = open(argv[1], O_CREAT | O_TRUNC | O_RDWR, 0600);
+	if (fd < 0) {
+		perror(argv[1]);
+		return 2;
+	}
+
+	/* Zero the project id and the extent size hint. */
+	ret = ioctl(fd, FS_IOC_FSGETXATTR, &fa);
+	if (ret) {
+		perror("FSGETXATTR check file");
+		return 2;
+	}
+
+	if (fa.fsx_projid != 0 || fa.fsx_extsize != 0) {
+		fa.fsx_projid = 0;
+		fa.fsx_extsize = 0;
+		ret = ioctl(fd, FS_IOC_FSSETXATTR, &fa);
+		if (ret) {
+			perror("FSSETXATTR zeroing");
+			return 2;
+		}
+	}
+
+	/* Dirty a few kb of a file to create delalloc extents. */
+	sz = write(fd, zerobuf, sizeof(zerobuf));
+	if (sz != sizeof(zerobuf)) {
+		perror("delalloc write");
+		return 2;
+	}
+
+	/*
+	 * The regression we're trying to test happens when the fsxattr input
+	 * validation decides to bail out after the chown quota reservation has
+	 * been made on a file containing delalloc extents.  Extent size hints
+	 * can't be set on non-empty files and we can't check the value until
+	 * we've reserved resources and taken the file's ILOCK, so this is a
+	 * perfect vector for triggering this condition.  In this way we set up
+	 * a FSSETXATTR call that will fail.
+	 */
+	ret = ioctl(fd, FS_IOC_FSGETXATTR, &fa);
+	if (ret) {
+		perror("FSGETXATTR");
+		return 2;
+	}
+
+	fa.fsx_projid = 23652;
+	fa.fsx_extsize = 2;
+	fa.fsx_xflags |= FS_XFLAG_EXTSIZE;
+
+	ret = ioctl(fd, FS_IOC_FSSETXATTR, &fa);
+	if (ret) {
+		printf("FSSETXATTRR should fail: %s\n", strerror(errno));
+		return 0;
+	}
+
+	/* Uhoh, that FSSETXATTR call should have failed! */
+	return 3;
+}
diff --git a/tests/xfs/765 b/tests/xfs/765
new file mode 100755
index 00000000..68b89ce3
--- /dev/null
+++ b/tests/xfs/765
@@ -0,0 +1,71 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0-or-later
+# Copyright (c) 2021 Oracle.  All Rights Reserved.
+#
+# FS QA Test No. 765
+#
+# Regression test for failing to undo delalloc quota reservations when changing
+# project id but we fail some other part of FSSETXATTR validation.  If we fail
+# the test, we trip debugging assertions in dmesg.  This is a regression test
+# for commit 1aecf3734a95 ("xfs: fix chown leaking delalloc quota blocks when
+# fssetxattr fails").
+
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1    # failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+	rm -f $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/quota
+
+# real QA test starts here
+_supported_fs xfs
+_require_command "$FILEFRAG_PROG" filefrag
+_require_test_program "chprojid_fail"
+_require_quota
+_require_scratch
+
+rm -f $seqres.full
+
+echo "Format filesystem" | tee -a $seqres.full
+_scratch_mkfs > $seqres.full
+_qmount_option 'prjquota'
+_qmount
+_require_prjquota $SCRATCH_DEV
+
+# Make sure that a regular buffered write produces delalloc reservations.
+$XFS_IO_PROG -f -c 'pwrite 0 64k' $SCRATCH_MNT/testy &> /dev/null
+$FILEFRAG_PROG -v $SCRATCH_MNT/testy 2>&1 | grep -q delalloc || \
+	_notrun "test requires delayed allocation writes"
+rm -f $SCRATCH_MNT/testy
+
+echo "Run test program"
+$XFS_QUOTA_PROG -f -x -c 'report -ap' $SCRATCH_MNT >> $seqres.full
+$here/src/chprojid_fail $SCRATCH_MNT/blah
+
+# The regression we're testing for is an accounting bug involving delalloc
+# reservations.  FSSETXATTR does not itself cause dirty data writeback, so we
+# assume that if the file still has delalloc extents, then it must have had
+# them when chprojid_fail was running, and therefore the test was set up
+# correctly.  There's a slight chance that background writeback can sneak in
+# and flush the file, but this should be a small enough gap.
+$FILEFRAG_PROG -v $SCRATCH_MNT/blah 2>&1 | grep -q delalloc || \
+	echo "file didn't get delalloc extents, test invalid?"
+
+# Make a note of current quota status for diagnostic purposes
+$XFS_QUOTA_PROG -f -x -c 'report -ap' $SCRATCH_MNT >> $seqres.full
+
+# success, all done
+status=0
+exit
diff --git a/tests/xfs/765.out b/tests/xfs/765.out
new file mode 100644
index 00000000..d5f8fc11
--- /dev/null
+++ b/tests/xfs/765.out
@@ -0,0 +1,4 @@
+QA output created by 765
+Format filesystem
+Run test program
+FSSETXATTRR should fail: Invalid argument
diff --git a/tests/xfs/group b/tests/xfs/group
index d7aafc94..84468d10 100644
--- a/tests/xfs/group
+++ b/tests/xfs/group
@@ -505,4 +505,5 @@
 760 auto quick rw collapse punch insert zero prealloc
 761 auto quick realtime
 763 auto quick rw realtime
+765 auto quick quota
 915 auto quick quota
