diff --git a/test/TEST-01-BASIC/Makefile b/test/TEST-01-BASIC/Makefile
index 3a212a07a9..34d7cc6cdf 100644
--- a/test/TEST-01-BASIC/Makefile
+++ b/test/TEST-01-BASIC/Makefile
@@ -1,4 +1,4 @@
-BUILD_DIR=$(exec ../../tools/find-build-dir.sh)
+BUILD_DIR=$(shell ../../tools/find-build-dir.sh)
 
 all setup clean run:
 	@basedir=../.. TEST_BASE_DIR=../ BUILD_DIR=$(BUILD_DIR) ./test.sh --$@
diff --git a/test/TEST-13-NSPAWN-SMOKE/Makefile b/test/TEST-13-NSPAWN-SMOKE/Makefile
index ddcbbc302f..7d74b1343a 100644
--- a/test/TEST-13-NSPAWN-SMOKE/Makefile
+++ b/test/TEST-13-NSPAWN-SMOKE/Makefile
@@ -1,4 +1,4 @@
-BUILD_DIR=$(exec ../../tools/find-build-dir.sh)
+BUILD_DIR=$(shell ../../tools/find-build-dir.sh)
 
 all setup run:
 	@basedir=../.. TEST_BASE_DIR=../ BUILD_DIR=$(BUILD_DIR) ./test.sh --$@
diff --git a/test/TEST-13-NSPAWN-SMOKE/test.sh b/test/TEST-13-NSPAWN-SMOKE/test.sh
index 239c7e0731..6a0cb42eaf 100755
--- a/test/TEST-13-NSPAWN-SMOKE/test.sh
+++ b/test/TEST-13-NSPAWN-SMOKE/test.sh
@@ -147,7 +147,7 @@ function run {
     # test --network-namespace-path works with a network namespace created by "ip netns"
     ip netns add nspawn_test
     _netns_opt="--network-namespace-path=/run/netns/nspawn_test"
-    UNIFIED_CGROUP_HIERARCHY="$1" SYSTEMD_NSPAWN_USE_CGNS="$2" SYSTEMD_NSPAWN_API_VFS_WRITABLE="$3" systemd-nspawn --register=no -D "$_root" "$_netns_opt" ip a | grep -E '^1: lo.*DOWN'
+    UNIFIED_CGROUP_HIERARCHY="$1" SYSTEMD_NSPAWN_USE_CGNS="$2" SYSTEMD_NSPAWN_API_VFS_WRITABLE="$3" systemd-nspawn --register=no -D "$_root" "$_netns_opt" /bin/ip a | grep -v -E '^1: lo.*UP'
     local r=$?
     ip netns del nspawn_test
 
diff --git a/test/TEST-17-UDEV-WANTS/Makefile b/test/TEST-17-UDEV-WANTS/Makefile
index 3a212a07a9..34d7cc6cdf 100644
--- a/test/TEST-17-UDEV-WANTS/Makefile
+++ b/test/TEST-17-UDEV-WANTS/Makefile
@@ -1,4 +1,4 @@
-BUILD_DIR=$(exec ../../tools/find-build-dir.sh)
+BUILD_DIR=$(shell ../../tools/find-build-dir.sh)
 
 all setup clean run:
 	@basedir=../.. TEST_BASE_DIR=../ BUILD_DIR=$(BUILD_DIR) ./test.sh --$@
diff --git a/test/TEST-18-FAILUREACTION/Makefile b/test/TEST-18-FAILUREACTION/Makefile
index 3a212a07a9..34d7cc6cdf 100644
--- a/test/TEST-18-FAILUREACTION/Makefile
+++ b/test/TEST-18-FAILUREACTION/Makefile
@@ -1,4 +1,4 @@
-BUILD_DIR=$(exec ../../tools/find-build-dir.sh)
+BUILD_DIR=$(shell ../../tools/find-build-dir.sh)
 
 all setup clean run:
 	@basedir=../.. TEST_BASE_DIR=../ BUILD_DIR=$(BUILD_DIR) ./test.sh --$@
diff --git a/test/TEST-19-DELEGATE/Makefile b/test/TEST-19-DELEGATE/Makefile
index 3a212a07a9..34d7cc6cdf 100644
--- a/test/TEST-19-DELEGATE/Makefile
+++ b/test/TEST-19-DELEGATE/Makefile
@@ -1,4 +1,4 @@
-BUILD_DIR=$(exec ../../tools/find-build-dir.sh)
+BUILD_DIR=$(shell ../../tools/find-build-dir.sh)
 
 all setup clean run:
 	@basedir=../.. TEST_BASE_DIR=../ BUILD_DIR=$(BUILD_DIR) ./test.sh --$@