diff --git a/sys/include/universal_address.h b/sys/include/universal_address.h
index ebc600fa3b..86525f4aad 100644
--- a/sys/include/universal_address.h
+++ b/sys/include/universal_address.h
@@ -27,8 +27,20 @@ extern "C" {
 
 #include <stdint.h>
 #include <stdlib.h>
+#include "net/ipv6/addr.h"
 
-#define UNIVERSAL_ADDRESS_SIZE (16)         /**< size of the used addresses in bytes */
+/** @brief  size of the used addresses in bytes */
+/* determine the widest possible address type */
+#ifndef UNIVERSAL_ADDRESS_SIZE
+#define UNIVERSAL_ADDRESS_SIZE (0)       /* rather senseless default, should
+                                            trigger warnings */
+#endif
+
+/* IPv6 address has 128 bit -> 16 bytes */
+#if defined(MODULE_IPV6_ADDR) && ((IPV6_ADDR_BIT_LEN >> 3) > UNIVERSAL_ADDRESS_SIZE)
+#undef UNIVERSAL_ADDRESS_SIZE
+#define UNIVERSAL_ADDRESS_SIZE (IPV6_ADDR_BIT_LEN >> 3)
+#endif
 
 /**
  * @brief The container descriptor used to identify a universal address entry
diff --git a/sys/universal_address/universal_address.c b/sys/universal_address/universal_address.c
index 6e08081691..ef0e0cf179 100644
--- a/sys/universal_address/universal_address.c
+++ b/sys/universal_address/universal_address.c
@@ -19,6 +19,12 @@
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
+#ifdef MODULE_FIB
+#include "net/fib.h"
+#ifdef MODULE_GNRC_IPV6
+#include "net/gnrc/ipv6.h"
+#endif
+#endif
 #include "mutex.h"
 
 #define ENABLE_DEBUG (0)
@@ -28,7 +34,17 @@
 /**
  * @brief Maximum number of entries handled
  */
-#define UNIVERSAL_ADDRESS_MAX_ENTRIES (40)
+/* determine the maximum numer of entries */
+#ifndef UNIVERSAL_ADDRESS_MAX_ENTRIES
+/* all potential users of universal addresses have to add their requirements here */
+#   if defined(MODULE_FIB) && defined(MODULE_GNRC_IPV6)
+#       define UA_ADD0 (2 * GNRC_IPV6_FIB_TABLE_SIZE)
+#   else
+#       define UA_ADD0  (0)
+#   endif
+
+#   define UNIVERSAL_ADDRESS_MAX_ENTRIES    (UA_ADD0)
+#endif
 
 /**
  * @brief counter indicating the number of entries allocated
diff --git a/tests/unittests/tests-fib/Makefile.include b/tests/unittests/tests-fib/Makefile.include
index 2c46289f2f..75e2535a55 100644
--- a/tests/unittests/tests-fib/Makefile.include
+++ b/tests/unittests/tests-fib/Makefile.include
@@ -1,3 +1,3 @@
-CFLAGS += -DFIB_DEVEL_HELPER
+CFLAGS += -DFIB_DEVEL_HELPER -DUNIVERSAL_ADDRESS_SIZE=16 -DUNIVERSAL_ADDRESS_MAX_ENTRIES=40
 
 USEMODULE += fib