diff --git a/libmuscle/fortran/build/libmuscle/tests/Makefile b/libmuscle/fortran/build/libmuscle/tests/Makefile
index 66afaf9f..6a75bc13 100644
--- a/libmuscle/fortran/build/libmuscle/tests/Makefile
+++ b/libmuscle/fortran/build/libmuscle/tests/Makefile
@@ -47,6 +47,10 @@ endif
 
 CPP_BUILD_DIR := $(CURDIR)/../../../../cpp/build
 
+LDFLAGS += -L../../ymmsl
+LDFLAGS += -L../../../../cpp/build/libmuscle
+LDFLAGS += -L../../../../cpp/build/ymmsl
+
 LDFLAGS += -pthread $(CURDIR)/../libmuscle_fortran.a $(CURDIR)/../../ymmsl/libymmsl_fortran.a
 LDFLAGS += $(CPP_BUILD_DIR)/libmuscle/libmuscle_d.a $(CPP_BUILD_DIR)/ymmsl/libymmsl_d.a