diff --git a/sys/include/net/gnrc/sixlowpan/config.h b/sys/include/net/gnrc/sixlowpan/config.h
index 8cfebbcf67..0e5d52ad59 100644
--- a/sys/include/net/gnrc/sixlowpan/config.h
+++ b/sys/include/net/gnrc/sixlowpan/config.h
@@ -68,6 +68,22 @@ extern "C" {
 #define GNRC_SIXLOWPAN_FRAG_RBUF_TIMEOUT_MS (3U * US_PER_SEC)
 #endif
 
+/**
+ * @brief   Aggressively override reassembly buffer when full
+ *
+ * @note    Only applicable with
+ *          [gnrc_sixlowpan_frag](@ref net_gnrc_sixlowpan_frag) module
+ *
+ * When set to a non-zero value this will cause the reassembly buffer to
+ * override the oldest entry no matter what. When set to zero only the oldest
+ * entry that is older than @ref GNRC_SIXLOWPAN_FRAG_RBUF_TIMEOUT_MS will be
+ * overwritten (they will still timeout normally if reassembly buffer is not
+ * full).
+ */
+#ifndef GNRC_SIXLOWPAN_FRAG_RBUF_AGGRESSIVE_OVERRIDE
+#define GNRC_SIXLOWPAN_FRAG_RBUF_AGGRESSIVE_OVERRIDE    (1)
+#endif
+
 /**
  * @brief   Registration lifetime in minutes for the address registration option
  *
diff --git a/sys/net/gnrc/network_layer/sixlowpan/frag/rbuf.c b/sys/net/gnrc/network_layer/sixlowpan/frag/rbuf.c
index fc2d16bacc..ea35516dfe 100644
--- a/sys/net/gnrc/network_layer/sixlowpan/frag/rbuf.c
+++ b/sys/net/gnrc/network_layer/sixlowpan/frag/rbuf.c
@@ -322,10 +322,17 @@ static rbuf_t *_rbuf_get(const void *src, size_t src_len,
         /* if oldest is not empty, res must not be NULL (because otherwise
          * oldest could have been picked as res) */
         assert(!rbuf_entry_empty(oldest));
-        DEBUG("6lo rfrag: reassembly buffer full, remove oldest entry\n");
-        gnrc_pktbuf_release(oldest->super.pkt);
-        rbuf_rm(oldest);
-        res = oldest;
+        if (GNRC_SIXLOWPAN_FRAG_RBUF_AGGRESSIVE_OVERRIDE ||
+            ((now_usec - oldest->arrival) >
+            GNRC_SIXLOWPAN_FRAG_RBUF_TIMEOUT_MS)) {
+            DEBUG("6lo rfrag: reassembly buffer full, remove oldest entry\n");
+            gnrc_pktbuf_release(oldest->super.pkt);
+            rbuf_rm(oldest);
+            res = oldest;
+        }
+        else {
+            return NULL;
+        }
     }
 
     /* now we have an empty spot */