diff --git a/include/maxscale/filter.hh b/include/maxscale/filter.hh
index 1cb9b90c2..513f8be9c 100644
--- a/include/maxscale/filter.hh
+++ b/include/maxscale/filter.hh
@@ -215,7 +215,7 @@ public:
     static MXS_FILTER_SESSION* newSession(MXS_FILTER* pInstance, MXS_SESSION* pSession)
     {
         FilterType* pFilter = static_cast<FilterType*>(pInstance);
-        FilterSessionType* pFilterSession;
+        FilterSessionType* pFilterSession = NULL;
 
         MXS_EXCEPTION_GUARD(pFilterSession = pFilter->newSession(pSession));
 
diff --git a/query_classifier/qc_sqlite/qc_sqlite.c b/query_classifier/qc_sqlite/qc_sqlite.c
index 0c15dc531..1fbb4981e 100644
--- a/query_classifier/qc_sqlite/qc_sqlite.c
+++ b/query_classifier/qc_sqlite/qc_sqlite.c
@@ -2991,7 +2991,7 @@ static int32_t qc_sqlite_process_init(void)
         {
             if (this_unit.log_level != QC_LOG_NOTHING)
             {
-                const char* message;
+                const char* message = NULL;
 
                 switch (this_unit.log_level)
                 {
diff --git a/server/core/buffer.c b/server/core/buffer.c
index 1c1dcab77..c0a3b354d 100644
--- a/server/core/buffer.c
+++ b/server/core/buffer.c
@@ -526,8 +526,8 @@ int gwbuf_compare(const GWBUF* lhs, const GWBUF* rhs)
 
             while ((rv == 0) && (i < llen))
             {
-                uint8_t lc;
-                uint8_t rc;
+                uint8_t lc = 0;
+                uint8_t rc = 0;
 
                 ss_debug(bool rv1 = ) gwbuf_get_byte(&lhs, &loffset, &lc);
                 ss_debug(bool rv2 = ) gwbuf_get_byte(&rhs, &roffset, &rc);
diff --git a/server/core/externcmd.c b/server/core/externcmd.c
index 8df3619bc..8a4ae5451 100644
--- a/server/core/externcmd.c
+++ b/server/core/externcmd.c
@@ -37,7 +37,7 @@ int tokenize_arguments(char* argstr, char** argv)
     bool escaped = false;
     char *ptr, *start;
     char args[strlen(argstr) + 1];
-    char qc;
+    char qc = 0;
 
     strcpy(args, argstr);
     start = args;
diff --git a/server/core/log_manager.cc b/server/core/log_manager.cc
index b106c4fba..358d2bc3b 100644
--- a/server/core/log_manager.cc
+++ b/server/core/log_manager.cc
@@ -751,11 +751,11 @@ static int logmanager_write_log(int            priority,
                                 size_t         str_len,
                                 const char*    str)
 {
-    logfile_t*   lf;
-    char*        wp;
+    logfile_t*   lf = NULL;
+    char*        wp = NULL;
     int          err = 0;
-    blockbuf_t*  bb;
-    blockbuf_t*  bb_c;
+    blockbuf_t*  bb = NULL;
+    blockbuf_t*  bb_c = NULL;
     size_t       timestamp_len;
     int          i;
 
diff --git a/server/core/modutil.c b/server/core/modutil.c
index 1ac172c4d..b96a504cd 100644
--- a/server/core/modutil.c
+++ b/server/core/modutil.c
@@ -797,7 +797,7 @@ char* strnchr_esc(char* ptr, char c, int len)
     char* p = (char*)ptr;
     char* start = p;
     bool quoted = false, escaped = false;
-    char qc;
+    char qc = 0;
 
     while (p < start + len)
     {
@@ -843,7 +843,7 @@ char* strnchr_esc_mysql(char* ptr, char c, int len)
     char* p = (char*) ptr;
     char* start = p, *end = start + len;
     bool quoted = false, escaped = false, backtick = false, comment = false;
-    char qc;
+    char qc = 0;
 
     while (p < end)
     {
diff --git a/server/core/poll.c b/server/core/poll.c
index bbc0ab076..bfc04e51d 100644
--- a/server/core/poll.c
+++ b/server/core/poll.c
@@ -1256,7 +1256,7 @@ void
 dShowThreads(DCB *dcb)
 {
     int i, j, n;
-    char *state;
+    char *state = NULL;
     double avg1 = 0.0, avg5 = 0.0, avg15 = 0.0;
     double qavg1 = 0.0, qavg5 = 0.0, qavg15 = 0.0;
 
diff --git a/server/core/server.c b/server/core/server.c
index c4f92500b..6916726a1 100644
--- a/server/core/server.c
+++ b/server/core/server.c
@@ -941,9 +941,9 @@ serverRowCallback(RESULTSET *set, void *data)
 {
     int *rowno = (int *)data;
     int i = 0;
-    char *stat, buf[20];
-    RESULT_ROW *row;
-    SERVER *server;
+    char *stat = NULL, buf[20];
+    RESULT_ROW *row = NULL;
+    SERVER *server = NULL;
 
     spinlock_acquire(&server_spin);
     server = allServers;
diff --git a/server/core/service.c b/server/core/service.c
index 4cc5f764b..d44805132 100644
--- a/server/core/service.c
+++ b/server/core/service.c
@@ -1210,8 +1210,8 @@ void serviceSetRetryOnFailure(SERVICE *service, char* value)
 bool
 serviceSetFilters(SERVICE *service, char *filters)
 {
-    MXS_FILTER_DEF **flist;
-    char *ptr, *brkt;
+    MXS_FILTER_DEF **flist = NULL;
+    char *ptr = NULL, *brkt = NULL;
     int n = 0;
     bool rval = true;
     uint64_t capabilities = 0;
diff --git a/server/core/utils.c b/server/core/utils.c
index b119b897f..265bfc3bc 100644
--- a/server/core/utils.c
+++ b/server/core/utils.c
@@ -957,7 +957,7 @@ int open_network_socket(enum mxs_socket_type type, struct sockaddr_storage *addr
     ss_dassert(type == MXS_SOCKET_NETWORK || type == MXS_SOCKET_LISTENER);
 #ifdef __USE_POSIX
     struct addrinfo *ai = NULL, hint = {};
-    int so, rc;
+    int so = 0, rc = 0;
     hint.ai_socktype = SOCK_STREAM;
     hint.ai_family = AF_UNSPEC;
     hint.ai_flags = AI_ALL;
diff --git a/server/modules/filter/cache/rules.cc b/server/modules/filter/cache/rules.cc
index 1983862f4..9c4a09a90 100644
--- a/server/modules/filter/cache/rules.cc
+++ b/server/modules/filter/cache/rules.cc
@@ -596,11 +596,11 @@ static CACHE_RULE *cache_rule_create_simple_user(cache_rule_attribute_t attribut
                                                  const char            *cvalue,
                                                  uint32_t               debug)
 {
+    CACHE_RULE *rule = NULL;
+
     ss_dassert(attribute == CACHE_ATTRIBUTE_USER);
     ss_dassert((op == CACHE_OP_EQ) || (op == CACHE_OP_NEQ));
 
-    CACHE_RULE *rule = NULL;
-
     bool error = false;
     size_t len = strlen(cvalue);
 
@@ -911,7 +911,7 @@ static CACHE_RULE *cache_rule_create_simple(cache_rule_attribute_t attribute,
 {
     ss_dassert((op == CACHE_OP_EQ) || (op == CACHE_OP_NEQ));
 
-    CACHE_RULE *rule;
+    CACHE_RULE *rule = NULL;
 
     switch (attribute)
     {
@@ -1526,7 +1526,7 @@ static bool cache_rule_matches_table_regexp(CACHE_RULE *self,
     bool matches = false;
 
     int n;
-    char **names;
+    char **names = NULL;
     bool fullnames;
 
     fullnames = true;
@@ -1612,7 +1612,7 @@ static bool cache_rule_matches_table_simple(CACHE_RULE *self, const char *defaul
     }
 
     int n;
-    char **names;
+    char **names = NULL;
 
     names = qc_get_table_names((GWBUF*)query, &n, fullnames);
 
diff --git a/server/modules/filter/dbfwfilter/dbfwfilter.c b/server/modules/filter/dbfwfilter/dbfwfilter.c
index 8955aba64..274b7a834 100644
--- a/server/modules/filter/dbfwfilter/dbfwfilter.c
+++ b/server/modules/filter/dbfwfilter/dbfwfilter.c
@@ -892,7 +892,7 @@ char* get_regex_string(char** saved)
 {
     char *start = NULL, *ptr = *saved;
     bool escaped = false, quoted = false;
-    char delimiter;
+    char delimiter = 0;
     while (*ptr != '\0')
     {
         if (!escaped)
diff --git a/server/modules/routing/debugcli/debugcmd.c b/server/modules/routing/debugcli/debugcmd.c
index a221874ca..8b7d732c3 100644
--- a/server/modules/routing/debugcli/debugcmd.c
+++ b/server/modules/routing/debugcli/debugcmd.c
@@ -1669,7 +1669,7 @@ static struct
 static unsigned long
 convert_arg(char *arg, int arg_type)
 {
-    unsigned long rval;
+    unsigned long rval = 0;
 
     switch (arg_type)
     {