diff --git a/sys/net/gnrc/network_layer/sixlowpan/iphc/gnrc_sixlowpan_iphc.c b/sys/net/gnrc/network_layer/sixlowpan/iphc/gnrc_sixlowpan_iphc.c
index 69bbdb6795..9903cf299c 100644
--- a/sys/net/gnrc/network_layer/sixlowpan/iphc/gnrc_sixlowpan_iphc.c
+++ b/sys/net/gnrc/network_layer/sixlowpan/iphc/gnrc_sixlowpan_iphc.c
@@ -454,6 +454,7 @@ void gnrc_sixlowpan_iphc_recv(gnrc_pktsnip_t *sixlo, void *rbuf_ptr,
             break;
 
         case IPHC_M_DAC_DAM_U_CTX_64:
+            assert(ctx != NULL);
             memcpy(ipv6_hdr->dst.u8 + 8, iphc_hdr + payload_offset, 8);
             ipv6_addr_init_prefix(&ipv6_hdr->dst, &ctx->prefix,
                                   ctx->prefix_len);
@@ -464,6 +465,7 @@ void gnrc_sixlowpan_iphc_recv(gnrc_pktsnip_t *sixlo, void *rbuf_ptr,
             ipv6_hdr->dst.u32[2] = byteorder_htonl(0x000000ff);
             ipv6_hdr->dst.u16[6] = byteorder_htons(0xfe00);
             memcpy(ipv6_hdr->dst.u8 + 14, iphc_hdr + payload_offset, 2);
+            assert(ctx != NULL);
             ipv6_addr_init_prefix(&ipv6_hdr->dst, &ctx->prefix,
                                   ctx->prefix_len);
             payload_offset += 2;
@@ -477,6 +479,7 @@ void gnrc_sixlowpan_iphc_recv(gnrc_pktsnip_t *sixlo, void *rbuf_ptr,
                 _recv_error_release(sixlo, ipv6, rbuf);
                 return;
             }
+            assert(ctx != NULL);
             ipv6_addr_init_prefix(&ipv6_hdr->dst, &ctx->prefix,
                                   ctx->prefix_len);
             break;
@@ -509,6 +512,7 @@ void gnrc_sixlowpan_iphc_recv(gnrc_pktsnip_t *sixlo, void *rbuf_ptr,
 
         case IPHC_M_DAC_DAM_M_UC_PREFIX:
             do {
+                assert(ctx != NULL);
                 uint8_t orig_ctx_len = ctx->prefix_len;
 
                 ipv6_addr_set_unspecified(&ipv6_hdr->dst);