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-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=$(BUILD_DIR) ./test.sh --$@