diff --git a/simgear/props/Makefile.am b/simgear/props/Makefile.am
index f1cf6f9a..f3ad95d0 100644
--- a/simgear/props/Makefile.am
+++ b/simgear/props/Makefile.am
@@ -20,6 +20,7 @@ props_test_LDADD = \
 	$(top_builddir)/simgear/xml/libsgxml.a \
 	$(top_builddir)/simgear/misc/libsgmisc.a \
 	$(top_builddir)/simgear/debug/libsgdebug.a \
-	$(top_builddir)/simgear/structure/libsgstructure.a
+	$(top_builddir)/simgear/structure/libsgstructure.a \
+	-lOpenThreads
 
 INCLUDES = -I$(top_srcdir)
diff --git a/simgear/sound/Makefile.am b/simgear/sound/Makefile.am
index c6273463..48381175 100644
--- a/simgear/sound/Makefile.am
+++ b/simgear/sound/Makefile.am
@@ -30,6 +30,7 @@ openal_test2_LDADD = \
 	$(top_builddir)/simgear/debug/libsgdebug.a \
 	$(top_builddir)/simgear/misc/libsgmisc.a \
 	$(top_builddir)/simgear/structure/libsgstructure.a \
-	$(openal_LIBS)
+	$(openal_LIBS) \
+	-lOpenThreads
 
 INCLUDES = -I$(top_srcdir) -DSRC_DIR=\"$(top_srcdir)/simgear/sound\"