diff --git a/src/backends/redis.c b/src/backends/redis.c
index 1b17c83..b61e60f 100644
--- a/src/backends/redis.c
+++ b/src/backends/redis.c
@@ -222,7 +222,9 @@ bool
 unban(cfg_t *cfg, const char *ip) {
   assert(cfg != NULL);
 
-  (void)(ip); /* suppress warning for unused variable 'ip' */
+  (void)(cfg); /* suppress warning for unused variable 'ip' */
+  (void)(ip);  /* suppress warning for unused variable 'ip' */
+
   return true;
 }
 
@@ -230,7 +232,9 @@ bool
 check(cfg_t *cfg, const char *ip) {
   assert(cfg != NULL);
 
-  (void)(ip); /* suppress warning for unused variable 'ip' */
+  (void)(cfg); /* suppress warning for unused variable 'ip' */
+  (void)(ip);  /* suppress warning for unused variable 'ip' */
+
   return false;
 }
 
diff --git a/src/client.c b/src/client.c
index 00998a5..2493ea4 100644
--- a/src/client.c
+++ b/src/client.c
@@ -117,7 +117,9 @@ int main(int argc, char *argv[]) {
   SA_REGISTER(SIGINT,  &signal_handler);
 
   /* prepare client side of socket */
-  mkstemp(opts.csocket_cpath);
+  ret = mkstemp(opts.csocket_cpath);
+  if (ret >= 0)
+    close(ret); /* suppress compiler warning */
   unlink(opts.csocket_cpath); /* remove regular file created by mkstemp() */
 
   if ((opts.csocket = f2b_csocket_connect(opts.csocket_spath, opts.csocket_cpath)) <= 0)
diff --git a/src/sources/files.c b/src/sources/files.c
index 6b208e7..5b46fa0 100644
--- a/src/sources/files.c
+++ b/src/sources/files.c
@@ -126,7 +126,12 @@ config(cfg_t *cfg, const char *key, const char *value) {
   assert(cfg != NULL);
   assert(key   != NULL);
   assert(value != NULL);
+
   /* no options */
+  (void)(cfg);   /* suppress warning for unused variable 'ip' */
+  (void)(key);   /* suppress warning for unused variable 'ip' */
+  (void)(value); /* suppress warning for unused variable 'ip' */
+
   return false;
 }
 
diff --git a/t/t_cmd.c b/t/t_cmd.c
index 573a34b..708ff53 100644
--- a/t/t_cmd.c
+++ b/t/t_cmd.c
@@ -5,6 +5,8 @@ int main() {
   char buf[1024];
   const char *line;
 
+  UNUSED(line);
+
   buf[0] = '\0';
   f2b_cmd_append_arg(buf, sizeof(buf), "42");
   assert(strcmp(buf, "42\n") == 0);
diff --git a/t/t_statefile.c b/t/t_statefile.c
index 06f081a..2f2ff90 100644
--- a/t/t_statefile.c
+++ b/t/t_statefile.c
@@ -11,6 +11,7 @@ int main() {
   struct stat st;
   time_t banned_at = 0, release_at = 0;
 
+  UNUSED(res);
   UNUSED(list);
 
   snprintf(jailname, sizeof(jailname), "%lu", time(NULL)); /* gen unique jailname */