diff --git a/Makefile.am b/Makefile.am
index 9a739b6..5df4bd1 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -101,6 +101,7 @@ tests/Transfer_-_--rate-limit.test \
 tests/Transfer_-_--remote.test \
 tests/Transfer_-_--stop-at-size.test \
 tests/Transfer_-_--stop-at-size_reads.test \
+tests/Watchfd_-_Multiple_arguments.test \
 tests/Watchfd_-_Multiple_descriptors.test \
 tests/Watchfd_-_Single_descriptor.test
 
diff --git a/tests/Memory_safety_-_Watchfd.test b/tests/Memory_safety_-_Watchfd.test
index 54c7f1f..6791397 100755
--- a/tests/Memory_safety_-_Watchfd.test
+++ b/tests/Memory_safety_-_Watchfd.test
@@ -65,4 +65,43 @@ pid=$!
 sleep 0.1
 { runWithValgrind -P "${workFile3}" -d "${pid}" -f -i 0.5 >/dev/null 2>&1; } 4>&1 || exit 1
 
+# Check "--watchfd PID1 PID2".
+seq 1 100 > "${workFile1}"
+seq 1 300 > "${workFile2}"
+true > "${workFile3}"
+# shellcheck disable=SC2030
+(
+while test -e "${workFile3}" && ! test -s "${workFile3}"; do sleep 0.1; done
+sleep 1
+read -r line
+exec 9<"${workFile2}"
+sleep 1
+exec 8<"${workFile1}"
+exec 7</dev/null
+sleep 1
+exec 9<&-
+# shellcheck disable=SC2034
+read -r line
+sleep 1
+) <"${workFile1}" &
+pid1=$!
+# shellcheck disable=SC2030
+(
+while test -e "${workFile3}" && ! test -s "${workFile3}"; do sleep 0.1; done
+sleep 1
+read -r line
+exec 9<"${workFile2}"
+sleep 1
+exec 8<"${workFile1}"
+exec 7</dev/null
+sleep 1
+exec 9<&-
+# shellcheck disable=SC2034
+read -r line
+sleep 1
+) <"${workFile1}" &
+pid2=$!
+sleep 0.1
+{ runWithValgrind -P "${workFile3}" -f -i 0.5 -d "${pid1}" "${pid2}" >/dev/null 2>&1; } 4>&1 || exit 1
+
 exit 0
diff --git a/tests/Watchfd_-_Multiple_arguments.test b/tests/Watchfd_-_Multiple_arguments.test
new file mode 100755
index 0000000..7428967
--- /dev/null
+++ b/tests/Watchfd_-_Multiple_arguments.test
@@ -0,0 +1,101 @@
+#!/bin/sh
+#
+# Check that watching a process's file descriptors works as expected when
+# given multiple arguments.
+
+# Allow all tests to be skipped, e.g. during a release build
+test "${SKIP_ALL_TESTS}" = "1" && exit 77
+
+true "${testSubject:?not set - call this from 'make check'}"
+true "${workFile1:?not set - call this from 'make check'}"
+true "${workFile2:?not set - call this from 'make check'}"
+true "${workFile3:?not set - call this from 'make check'}"
+true "${workFile4:?not set - call this from 'make check'}"
+
+# Skip the test if "-d" is not available.
+if ! "${testSubject}" -h | grep -Fq ' -d'; then
+	echo "no \`--watchfd' / \`-d' option on this platform"
+	exit 77
+fi
+
+seq 1 100 > "${workFile1}"
+seq 1 300 > "${workFile2}"
+
+# Run two background processes to perform a few reads from a file.
+#
+# Each one only starts doing anything once the PV process below has started
+# (the workFile3 check).
+true > "${workFile3}"
+(
+while test -e "${workFile3}" && ! test -s "${workFile3}"; do sleep 0.1; done
+sleep 1
+# shellcheck disable=SC2034 # line is deliberately unused
+read -r line <&8
+sleep 1
+) <&- 8<"${workFile1}" &
+pid1=$!
+
+(
+while test -e "${workFile3}" && ! test -s "${workFile3}"; do sleep 0.1; done
+sleep 1
+# shellcheck disable=SC2034 # line is deliberately unused
+read -r line <&9
+sleep 1
+) <&- 9<"${workFile2}" &
+pid2=$!
+
+sleep 0.1
+"${testSubject}" -P "${workFile3}" -f -i 0.5 -d "${pid1}" "${pid2}" >/dev/null 2>"${workFile4}"
+
+# Skip the test if "-d" does not work.
+if grep -Fq ' -d: not available' "${workFile4}"; then
+	echo "no \`--watchfd' / \`-d' option on this platform"
+	exit 77
+fi
+
+# Process the output to make it easier to handle.
+# NB "ESC [ A" is "cursor up", we turn that into "-" and a newline.
+tr '\r' '\n' < "${workFile4}" | sed 's/.\[A/-!/g' | tr '!' '\n' > "${workFile1}"
+
+# We should see at least 2 file positions for fd 8.
+positionsReported="$(awk '/^[0-9 ]+: *8:/ {print $3}' < "${workFile1}" | sort -n | uniq)"
+differentNumbers="$(printf "%s\n" "${positionsReported}" | grep -Ec .)"
+if ! test "${differentNumbers}" -gt 1; then
+	printf "%s\n" "Expected at least 2 different numbers to be output for fd 8"
+	printf "%s:\n%s\n" "Positions reported" "${positionsReported}"
+	printf "%s: %s\n" "Number of different values seen" "${differentNumbers}"
+	printf "%s\n" "Raw output:"
+	cat "${workFile1}"
+	exit 1
+fi
+
+# We should see at least 2 file positions for fd 9.
+positionsReported="$(awk '/^[0-9 ]+: *9:/ {print $3}' < "${workFile1}" | sort -n | uniq)"
+differentNumbers="$(printf "%s\n" "${positionsReported}" | grep -Ec .)"
+if ! test "${differentNumbers}" -gt 1; then
+	printf "%s\n" "Expected at least 2 different numbers to be output for fd 9"
+	printf "%s:\n%s\n" "Positions reported" "${positionsReported}"
+	printf "%s: %s\n" "Number of different values seen" "${differentNumbers}"
+	printf "%s\n" "Raw output:"
+	cat "${workFile1}"
+	exit 1
+fi
+
+# We should see the last 6 characters of fd 8's filename appear.
+lastChars="$(printf "%s\n" "${workFile1}" | rev | cut -b1-6 | rev)"
+if ! grep -Fq "${lastChars}:" < "${workFile1}"; then
+	printf "%s\n" "Expected to see a filename for fd 8"
+	printf "%s\n" "Raw output:"
+	cat "${workFile1}"
+	exit 1
+fi
+# We should see the last 6 characters of fd 9's filename appear.
+lastChars="$(printf "%s\n" "${workFile2}" | rev | cut -b1-6 | rev)"
+if ! grep -Fq "${lastChars}:" < "${workFile1}"; then
+	printf "%s\n" "Expected to see a filename for fd 9"
+	printf "%s\n" "Raw output:"
+	cat "${workFile1}"
+	exit 1
+fi
+
+exit 0