diff --git a/src/libstrongswan/tests/Makefile.am b/src/libstrongswan/tests/Makefile.am
index 331a5480d..b5fb45a1f 100644
--- a/src/libstrongswan/tests/Makefile.am
+++ b/src/libstrongswan/tests/Makefile.am
@@ -52,7 +52,7 @@ tests_SOURCES = tests.h tests.c \
 tests_CFLAGS = \
   -I$(top_srcdir)/src/libstrongswan \
   -I$(top_srcdir)/src/libstrongswan/tests \
-  -DPLUGINDIR=\""$(top_builddir)/src/libstrongswan/plugins\"" \
+  -DPLUGINDIR=\""$(abs_top_builddir)/src/libstrongswan/plugins\"" \
   -DPLUGINS=\""${s_plugins}\"" \
   @COVERAGE_CFLAGS@
 
diff --git a/src/libtls/tests/Makefile.am b/src/libtls/tests/Makefile.am
index 1c0e2f941..456383f02 100644
--- a/src/libtls/tests/Makefile.am
+++ b/src/libtls/tests/Makefile.am
@@ -11,7 +11,7 @@ tls_tests_CFLAGS = \
 	-I$(top_srcdir)/src/libtls \
 	-I$(top_srcdir)/src/libstrongswan \
 	-I$(top_srcdir)/src/libstrongswan/tests \
-	-DPLUGINDIR=\""$(top_builddir)/src/libstrongswan/plugins\"" \
+	-DPLUGINDIR=\""$(abs_top_builddir)/src/libstrongswan/plugins\"" \
 	-DPLUGINS=\""${s_plugins}\"" \
 	@COVERAGE_CFLAGS@