diff --git a/sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c b/sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c
index 07666aa2a870ba227cda0a6e9cd02e1968f13659..cdb30c90901baf60e1e8e383f855d56b499ecae3 100644
--- a/sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c
+++ b/sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c
@@ -59,9 +59,7 @@ static fib_entry_t _fib_entries[GNRC_IPV6_FIB_TABLE_SIZE];
 fib_table_t gnrc_ipv6_fib_table;
 #endif
 
-#if ENABLE_DEBUG
 static char addr_str[IPV6_ADDR_MAX_STR_LEN];
-#endif
 
 kernel_pid_t gnrc_ipv6_pid = KERNEL_PID_UNDEF;
 
diff --git a/sys/net/gnrc/network_layer/ipv6/hdr/gnrc_ipv6_hdr.c b/sys/net/gnrc/network_layer/ipv6/hdr/gnrc_ipv6_hdr.c
index 4d3295294d7d879232ec64c6f92aad88c40d8f7b..3310882c70a2565e7916042f0acbb70d4395ae1e 100644
--- a/sys/net/gnrc/network_layer/ipv6/hdr/gnrc_ipv6_hdr.c
+++ b/sys/net/gnrc/network_layer/ipv6/hdr/gnrc_ipv6_hdr.c
@@ -21,7 +21,7 @@
 #define ENABLE_DEBUG    (0)
 #include "debug.h"
 
-#if ENABLE_DEBUG && defined(MODULE_IPV6_ADDR)
+#if defined(MODULE_IPV6_ADDR)
 static char addr_str[IPV6_ADDR_MAX_STR_LEN];
 #endif
 
diff --git a/sys/net/gnrc/network_layer/ipv6/whitelist/gnrc_ipv6_whitelist.c b/sys/net/gnrc/network_layer/ipv6/whitelist/gnrc_ipv6_whitelist.c
index 6cfa72c06a61e3acd7a17cb8e8566cf6a43bc96e..a29e768adc95743f149201fb1c8f2f380232d8f5 100644
--- a/sys/net/gnrc/network_layer/ipv6/whitelist/gnrc_ipv6_whitelist.c
+++ b/sys/net/gnrc/network_layer/ipv6/whitelist/gnrc_ipv6_whitelist.c
@@ -24,9 +24,7 @@
 ipv6_addr_t gnrc_ipv6_whitelist[GNRC_IPV6_WHITELIST_SIZE];
 BITFIELD(gnrc_ipv6_whitelist_set, GNRC_IPV6_WHITELIST_SIZE);
 
-#if ENABLE_DEBUG
 static char addr_str[IPV6_ADDR_MAX_STR_LEN];
-#endif
 
 int gnrc_ipv6_whitelist_add(const ipv6_addr_t *addr)
 {
diff --git a/sys/net/gnrc/network_layer/ndp/gnrc_ndp.c b/sys/net/gnrc/network_layer/ndp/gnrc_ndp.c
index 4228d8dbf3b1e153192d39228a8084074189961f..7373d454be2fa1829e97de2829e300cee934c8cd 100644
--- a/sys/net/gnrc/network_layer/ndp/gnrc_ndp.c
+++ b/sys/net/gnrc/network_layer/ndp/gnrc_ndp.c
@@ -26,9 +26,10 @@
 #define ENABLE_DEBUG    (0)
 #include "debug.h"
 
-#if ENABLE_DEBUG
+/* For PRIu8 etc. */
+#include <inttypes.h>
+
 static char addr_str[IPV6_ADDR_MAX_STR_LEN];
-#endif
 
 gnrc_pktsnip_t *gnrc_ndp_nbr_sol_build(const ipv6_addr_t *tgt,
                                        gnrc_pktsnip_t *options)
diff --git a/sys/net/gnrc/network_layer/sixlowpan/ctx/gnrc_sixlowpan_ctx.c b/sys/net/gnrc/network_layer/sixlowpan/ctx/gnrc_sixlowpan_ctx.c
index 6af3cf4fd7904da240b55fb40afa6f05ddf16bff..6985a2fabadef56e1ac3d932470e52f645988185 100644
--- a/sys/net/gnrc/network_layer/sixlowpan/ctx/gnrc_sixlowpan_ctx.c
+++ b/sys/net/gnrc/network_layer/sixlowpan/ctx/gnrc_sixlowpan_ctx.c
@@ -29,9 +29,7 @@ static mutex_t _ctx_mutex = MUTEX_INIT;
 static uint32_t _current_minute(void);
 static void _update_lifetime(uint8_t id);
 
-#if ENABLE_DEBUG
 static char ipv6str[IPV6_ADDR_MAX_STR_LEN];
-#endif
 
 static inline bool _valid(uint8_t id)
 {
diff --git a/sys/net/gnrc/network_layer/sixlowpan/frag/gnrc_sixlowpan_frag.c b/sys/net/gnrc/network_layer/sixlowpan/frag/gnrc_sixlowpan_frag.c
index 0f47980c56efc477f50d60da169646a8a9322cca..faf991f30e8be8b6b779b526c7a6fde20e7e940c 100644
--- a/sys/net/gnrc/network_layer/sixlowpan/frag/gnrc_sixlowpan_frag.c
+++ b/sys/net/gnrc/network_layer/sixlowpan/frag/gnrc_sixlowpan_frag.c
@@ -225,7 +225,7 @@ void gnrc_sixlowpan_frag_send(gnrc_sixlowpan_msg_frag_t *fragment_msg)
     size_t payload_len = gnrc_pkt_len(fragment_msg->pkt->next);
     msg_t msg;
 
-#if defined(DEVELHELP) && defined(ENABLE_DEBUG)
+#if defined(DEVELHELP) && ENABLE_DEBUG
     if (iface == NULL) {
         DEBUG("6lo frag: iface == NULL, expect segmentation fault.\n");
         /* remove original packet from packet buffer */
diff --git a/sys/net/gnrc/network_layer/sixlowpan/frag/rbuf.c b/sys/net/gnrc/network_layer/sixlowpan/frag/rbuf.c
index 271d4887aa1742809534a5737fa4caea3f636c4f..13c853b063f7dff6bd74649f4bb3b69bf7c94058 100644
--- a/sys/net/gnrc/network_layer/sixlowpan/frag/rbuf.c
+++ b/sys/net/gnrc/network_layer/sixlowpan/frag/rbuf.c
@@ -46,9 +46,7 @@ static rbuf_int_t rbuf_int[RBUF_INT_SIZE];
 
 static rbuf_t rbuf[RBUF_SIZE];
 
-#if ENABLE_DEBUG
 static char l2addr_str[3 * RBUF_L2ADDR_MAX_LEN];
-#endif
 
 /* ------------------------------------
  * internal function definitions
diff --git a/sys/net/gnrc/routing/rpl/gnrc_rpl_control_messages.c b/sys/net/gnrc/routing/rpl/gnrc_rpl_control_messages.c
index 4dea2523d32bc3838153a23652c2d1ed16a32c08..47fad77e5b9e295a03626df57fb70219dfbec486 100644
--- a/sys/net/gnrc/routing/rpl/gnrc_rpl_control_messages.c
+++ b/sys/net/gnrc/routing/rpl/gnrc_rpl_control_messages.c
@@ -42,9 +42,7 @@
 #define ENABLE_DEBUG    (0)
 #include "debug.h"
 
-#if ENABLE_DEBUG
 static char addr_str[IPV6_ADDR_MAX_STR_LEN];
-#endif
 
 #define GNRC_RPL_GROUNDED_SHIFT             (7)
 #define GNRC_RPL_MOP_SHIFT                  (3)
@@ -465,8 +463,8 @@ bool _parse_options(int msg_type, gnrc_rpl_instance_t *inst, gnrc_rpl_opt_t *opt
                     first_target = target;
                 }
 
-                DEBUG("RPL: adding FT entry %s/%d 0x%" PRIx32 "\n",
-                      ipv6_addr_to_str(addr_str, &(target->target), sizeof(addr_str)),
+                DEBUG("RPL: adding FT entry %s/%d\n",
+                      ipv6_addr_to_str(addr_str, &(target->target), (unsigned)sizeof(addr_str)),
                       target->prefix_length);
 
                 gnrc_ipv6_nib_ft_add(&(target->target), target->prefix_length, src,
diff --git a/sys/net/gnrc/routing/rpl/gnrc_rpl_dodag.c b/sys/net/gnrc/routing/rpl/gnrc_rpl_dodag.c
index 81197b16cb64ed49eb07d42108b5568b00adb441..4b4021a2efd1ff0e5f04c2d55e9ba26af8ab7a0c 100644
--- a/sys/net/gnrc/routing/rpl/gnrc_rpl_dodag.c
+++ b/sys/net/gnrc/routing/rpl/gnrc_rpl_dodag.c
@@ -32,9 +32,7 @@
 #define ENABLE_DEBUG    (0)
 #include "debug.h"
 
-#if ENABLE_DEBUG
 static char addr_str[IPV6_ADDR_MAX_STR_LEN];
-#endif
 
 static gnrc_rpl_parent_t *_gnrc_rpl_find_preferred_parent(gnrc_rpl_dodag_t *dodag);