diff --git a/src/config.c b/src/config.c
index ff1f497..7953efa 100644
--- a/src/config.c
+++ b/src/config.c
@@ -12,7 +12,7 @@ f2b_config_param_create(const char *src) {
   size_t len;
 
   strncpy(line, src, sizeof(line));
-  line[CONFIG_LINE_MAX] = '\0';
+  line[CONFIG_LINE_MAX - 1] = '\0';
 
   /* strip spaces before key */
   key = line;
@@ -47,18 +47,18 @@ f2b_config_param_create(const char *src) {
   p++, *p = '\0';
 
   len = strlen(key);
-  if (len < 1 || len > CONFIG_KEY_MAX)
+  if (len < 1 || len >= CONFIG_KEY_MAX)
     return NULL;
 
   len = strlen(value);
-  if (len < 1 || len > CONFIG_VAL_MAX)
+  if (len < 1 || len >= CONFIG_VAL_MAX)
     return NULL;
 
   if ((param = calloc(1, sizeof(f2b_config_param_t))) != NULL) {
     strncpy(param->name,  key,   sizeof(param->name));
     strncpy(param->value, value, sizeof(param->value));
-    param->name[CONFIG_KEY_MAX] = '\0';
-    param->name[CONFIG_VAL_MAX] = '\0';
+    param->name [CONFIG_KEY_MAX - 1] = '\0';
+    param->value[CONFIG_VAL_MAX - 1] = '\0';
     return param;
   }
 
@@ -109,7 +109,7 @@ f2b_config_section_create(const char *src) {
 
   src++;
   strncpy(line, src, sizeof(line));
-  line[CONFIG_LINE_MAX] = '\0';
+  line[CONFIG_LINE_MAX - 1] = '\0';
 
   if ((end = strchr(line, ']')) == NULL)
     return NULL;
diff --git a/src/config.h b/src/config.h
index 6c367c3..f015293 100644
--- a/src/config.h
+++ b/src/config.h
@@ -17,8 +17,8 @@ typedef enum f2b_section_type {
 
 typedef struct f2b_config_param_t {
   struct f2b_config_param_t *next;
-  char name[CONFIG_KEY_MAX + 1];
-  char value[CONFIG_VAL_MAX + 1];
+  char name[CONFIG_KEY_MAX];
+  char value[CONFIG_VAL_MAX];
 } f2b_config_param_t;
 
 typedef struct f2b_config_section_t {
diff --git a/src/filters/preg.c b/src/filters/preg.c
index a122fef..263aa46 100644
--- a/src/filters/preg.c
+++ b/src/filters/preg.c
@@ -29,7 +29,7 @@ create(const char *id) {
   if ((cfg = calloc(1, sizeof(cfg_t))) == NULL)
     return NULL;
   strncpy(cfg->id, id, sizeof(cfg->id));
-  cfg->id[sizeof(cfg->id)] = '\0';
+  cfg->id[sizeof(cfg->id) - 1] = '\0';
 
   return cfg;
 }
@@ -113,6 +113,7 @@ match(cfg_t *cfg, const char *line, char *buf, size_t buf_size) {
     assert(buf_size > match_len);
     strncpy(buf, &line[match[1].rm_so], match_len);
     buf[match_len] = '\0';
+    buf[buf_size]  = '\0';
     return true;
   }