diff --git a/lib/Makefile.villas-ext.inc b/lib/Makefile.villas-ext.inc
index bf389b520..b8558a46a 100644
--- a/lib/Makefile.villas-ext.inc
+++ b/lib/Makefile.villas-ext.inc
@@ -30,7 +30,7 @@ LIBEXT_SRCS += $(addprefix lib/, sample.c queue.c queue_signalled.c \
                )
 
 LIBEXT_LDFLAGS = -shared
-LIBEXT_LDLIBS =
+LIBEXT_LDLIBS +=
 
 ifeq ($(PLATFORM),Linux)
 	LIBEXT_LDLIBS += -ldl -lrt -Wl,-soname,$(LIBEXT_NAME).so.$(LIBEXT_ABI_VERSION)
diff --git a/lib/Makefile.villas.inc b/lib/Makefile.villas.inc
index de6088bd2..766d44a99 100644
--- a/lib/Makefile.villas.inc
+++ b/lib/Makefile.villas.inc
@@ -36,8 +36,8 @@ LIB_SRCS += $(addprefix lib/kernel/, kernel.c rt.c) \
                log_helper.c io_format.c task.c buffer.c table.c bitset.c \
             )
 
-LIB_LDFLAGS = -shared
-LIB_LDLIBS  = $(LDLIBS)
+LIB_LDFLAGS += -shared
+LIB_LDLIBS  += $(LDLIBS)
 
 ifeq ($(PLATFORM),Linux)
 	LIB_LDLIBS += -ldl -lrt -Wl,-soname,$(LIB_NAME).so.$(LIB_ABI_VERSION)