diff --git a/contrib/apps/shell/shell.c b/contrib/apps/shell/shell.c
index 5ecbda0e..f4f668d7 100644
--- a/contrib/apps/shell/shell.c
+++ b/contrib/apps/shell/shell.c
@@ -160,7 +160,7 @@ static struct stats_proto* shell_stat_proto_stats[] = {
   &lwip_stats.tcp,
 #endif
 };
-const size_t num_protostats = sizeof(shell_stat_proto_stats)/sizeof(struct stats_proto*);
+static const size_t num_protostats = sizeof(shell_stat_proto_stats)/sizeof(struct stats_proto*);
 
 static const char *stat_msgs_proto[] = {
   " * transmitted ",
diff --git a/contrib/apps/socket_examples/socket_examples.c b/contrib/apps/socket_examples/socket_examples.c
index e7af5ee3..a60156f0 100644
--- a/contrib/apps/socket_examples/socket_examples.c
+++ b/contrib/apps/socket_examples/socket_examples.c
@@ -31,7 +31,7 @@
 #define SOCKET_EXAMPLES_RUN_PARALLEL 0
 #endif
 
-const u8_t cmpbuf[8] = {0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab};
+static const u8_t cmpbuf[8] = {0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab};
 
 /* a helper struct to ensure memory before/after fd_set is not touched */
 typedef struct _xx
diff --git a/src/api/api_msg.c b/src/api/api_msg.c
index b06f5f2f..8092be96 100644
--- a/src/api/api_msg.c
+++ b/src/api/api_msg.c
@@ -93,7 +93,7 @@ static void netconn_drain(struct netconn *conn);
 #endif /* LWIP_TCPIP_CORE_LOCKING */
 
 #if LWIP_NETCONN_FULLDUPLEX
-const u8_t netconn_deleted = 0;
+static const u8_t netconn_deleted = 0;
 
 int
 lwip_netconn_is_deallocated_msg(void *msg)
@@ -106,9 +106,9 @@ lwip_netconn_is_deallocated_msg(void *msg)
 #endif /* LWIP_NETCONN_FULLDUPLEX */
 
 #if LWIP_TCP
-const u8_t netconn_aborted = 0;
-const u8_t netconn_reset = 0;
-const u8_t netconn_closed = 0;
+static const u8_t netconn_aborted = 0;
+static const u8_t netconn_reset = 0;
+static const u8_t netconn_closed = 0;
 
 /** Translate an error to a unique void* passed via an mbox */
 static void *
diff --git a/src/apps/http/makefsdata/makefsdata.c b/src/apps/http/makefsdata/makefsdata.c
index 707d06f4..240c72e4 100644
--- a/src/apps/http/makefsdata/makefsdata.c
+++ b/src/apps/http/makefsdata/makefsdata.c
@@ -108,8 +108,8 @@ static int deflate_level; /* default compression level, can be changed via comma
 #include "../core/def.c"
 
 /** (Your server name here) */
-const char *serverID = "Server: "HTTPD_SERVER_AGENT"\r\n";
-char serverIDBuffer[1024];
+static const char *serverID = "Server: "HTTPD_SERVER_AGENT"\r\n";
+static char serverIDBuffer[1024];
 
 /* change this to suit your MEM_ALIGNMENT */
 #define PAYLOAD_ALIGNMENT 4
@@ -144,26 +144,26 @@ static int file_can_be_compressed(const char* filename);
 /* 5 bytes per char + 3 bytes per line */
 static char file_buffer_c[COPY_BUFSIZE * 5 + ((COPY_BUFSIZE / HEX_BYTES_PER_LINE) * 3)];
 
-char curSubdir[MAX_PATH_LEN-3];
-char lastFileVar[MAX_PATH_LEN];
-char hdr_buf[4096];
+static char curSubdir[MAX_PATH_LEN-3];
+static char lastFileVar[MAX_PATH_LEN];
+static char hdr_buf[4096];
 
-unsigned char processSubs = 1;
-unsigned char includeHttpHeader = 1;
-unsigned char useHttp11 = 0;
-unsigned char supportSsi = 1;
-unsigned char precalcChksum = 0;
-unsigned char includeLastModified = 0;
+static unsigned char processSubs = 1;
+static unsigned char includeHttpHeader = 1;
+static unsigned char useHttp11 = 0;
+static unsigned char supportSsi = 1;
+static unsigned char precalcChksum = 0;
+static unsigned char includeLastModified = 0;
 #if MAKEFS_SUPPORT_DEFLATE
-unsigned char deflateNonSsiFiles = 0;
-size_t deflatedBytesReduced = 0;
-size_t overallDataBytes = 0;
+static unsigned char deflateNonSsiFiles = 0;
+static size_t deflatedBytesReduced = 0;
+static size_t overallDataBytes = 0;
 #endif
-const char *exclude_list = NULL;
-const char *ncompress_list = NULL;
+static const char *exclude_list = NULL;
+static const char *ncompress_list = NULL;
 
-struct file_entry *first_file = NULL;
-struct file_entry *last_file = NULL;
+static struct file_entry *first_file = NULL;
+static struct file_entry *last_file = NULL;
 
 static char *ssi_file_buffer;
 static char **ssi_file_lines;
diff --git a/src/core/ipv4/dhcp.c b/src/core/ipv4/dhcp.c
index 4b3c479d..ba3ef355 100644
--- a/src/core/ipv4/dhcp.c
+++ b/src/core/ipv4/dhcp.c
@@ -160,11 +160,11 @@ enum dhcp_option_idx {
 
 /** Holds the decoded option values, only valid while in dhcp_recv.
     @todo: move this into struct dhcp? */
-u32_t dhcp_rx_options_val[DHCP_OPTION_IDX_MAX];
+static u32_t dhcp_rx_options_val[DHCP_OPTION_IDX_MAX];
 /** Holds a flag which option was received and is contained in dhcp_rx_options_val,
     only valid while in dhcp_recv.
     @todo: move this into struct dhcp? */
-u8_t  dhcp_rx_options_given[DHCP_OPTION_IDX_MAX];
+static u8_t  dhcp_rx_options_given[DHCP_OPTION_IDX_MAX];
 
 static u8_t dhcp_discover_request_options[] = {
   DHCP_OPTION_SUBNET_MASK,
diff --git a/src/core/ipv6/nd6.c b/src/core/ipv6/nd6.c
index d4673ca6..3b13c21e 100644
--- a/src/core/ipv6/nd6.c
+++ b/src/core/ipv6/nd6.c
@@ -96,7 +96,7 @@ u32_t reachable_time = LWIP_ND6_REACHABLE_TIME;
 u32_t retrans_timer = LWIP_ND6_RETRANS_TIMER; /* @todo implement this value in timer */
 
 #if LWIP_ND6_QUEUEING
-u8_t nd6_queue_size = 0;
+static u8_t nd6_queue_size = 0;
 #endif
 
 /* Index for cache entries. */
diff --git a/src/netif/bridgeif.c b/src/netif/bridgeif.c
index 8a97bce3..021922f6 100644
--- a/src/netif/bridgeif.c
+++ b/src/netif/bridgeif.c
@@ -120,7 +120,7 @@ typedef struct bridgeif_private_s {
 } bridgeif_private_t;
 
 /* netif data index to get the bridge on input */
-u8_t bridgeif_netif_client_id = 0xff;
+static u8_t bridgeif_netif_client_id = 0xff;
 
 /**
  * @ingroup bridgeif