diff --git a/bin/df/df.c b/bin/df/df.c
--- a/bin/df/df.c
+++ b/bin/df/df.c
@@ -84,7 +84,8 @@
 	return (a > b ? a : b);
 }
 
-static int	  aflag = 0, cflag, hflag, iflag, kflag, lflag = 0, nflag, Tflag;
+static int	  aflag = 0, cflag, hflag, iflag, kflag, lflag = 0, nflag,
+		  Pflag = 0, Tflag;
 static int	  thousands;
 static int	  skipvfs_l, skipvfs_t;
 static const char **vfslist_l, **vfslist_t;
@@ -125,6 +126,7 @@
 		case 'b':
 				/* FALLTHROUGH */
 		case 'P':
+			Pflag = 1;
 			/*
 			 * POSIX specifically discusses the behavior of
 			 * both -k and -P. It states that the blocksize should
@@ -462,7 +464,7 @@
 	static int headerlen, timesthrough = 0;
 	static const char *header;
 	int64_t used, availblks, inodes;
-	const char *format;
+	const char *availheader, *format;
 
 	if (++timesthrough == 1) {
 		mwp->mntfrom = imax(mwp->mntfrom, (int)strlen("Filesystem"));
@@ -483,14 +485,15 @@
 			mwp->total = imax(mwp->total, headerlen);
 		}
 		mwp->used = imax(mwp->used, (int)strlen("Used"));
-		mwp->avail = imax(mwp->avail, (int)strlen("Avail"));
+		availheader = Pflag ? "Available" : "Avail";
+		mwp->avail = imax(mwp->avail, (int)strlen(availheader));
 
 		xo_emit("{T:/%-*s}", mwp->mntfrom, "Filesystem");
 		if (Tflag)
 			xo_emit("  {T:/%-*s}", mwp->fstype, "Type");
 		xo_emit(" {T:/%*s} {T:/%*s} {T:/%*s} {T:Capacity}",
 			mwp->total, header,
-			mwp->used, "Used", mwp->avail, "Avail");
+			mwp->used, "Used", mwp->avail, availheader);
 		if (iflag) {
 			mwp->iused = imax(hflag ? 0 : mwp->iused,
 			    (int)strlen("  iused"));
diff --git a/bin/df/tests/Makefile b/bin/df/tests/Makefile
--- a/bin/df/tests/Makefile
+++ b/bin/df/tests/Makefile
@@ -1,6 +1,7 @@
 PACKAGE=	tests
 
-ATF_TESTS_SH=	t_df
+ATF_TESTS_SH=	df_test
+ATF_TESTS_SH+=	t_df
 
 PROGS+=		h_df
 BINDIR.h_df=	${TESTSDIR}
diff --git a/bin/df/tests/df_test.sh b/bin/df/tests/df_test.sh
new file mode 100644
--- /dev/null
+++ b/bin/df/tests/df_test.sh
@@ -0,0 +1,41 @@
+#
+# Copyright (c) 2025 Jose Luis Duran <jlduran@FreeBSD.org>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+
+atf_test_case Pflag
+Pflag_head()
+{
+	atf_set "descr" "Tests the output of df when using the -P flag"
+}
+Pflag_body()
+{
+	cat >expout <<EOF
+Filesystem   512-blocks        Used   Available Capacity  Mounted on
+filer:/      2405433344      270336  2405163008     1%    /filer
+EOF
+	atf_check -s exit:0 -o file:expout -e empty \
+	    -x "$(atf_get_srcdir)/h_df -P | head -2"
+}
+
+atf_test_case kPflags
+kPflags_head()
+{
+	atf_set "descr" "Tests the output of df when using the -k and -P flags"
+}
+kPflags_body()
+{
+	cat >expout <<EOF
+Filesystem  1024-blocks        Used   Available Capacity  Mounted on
+filer:/      1202716672      135168  1202581504     1%    /filer
+EOF
+	atf_check -s exit:0 -o file:expout -e empty \
+	    -x "$(atf_get_srcdir)/h_df -k -P | head -2"
+}
+
+atf_init_test_cases()
+{
+	atf_add_test_case Pflag
+	atf_add_test_case kPflags
+}