diff --git a/src/filters/filter.h b/src/filters/filter.h
index 3b37d32..3aedb5a 100644
--- a/src/filters/filter.h
+++ b/src/filters/filter.h
@@ -5,6 +5,7 @@
 typedef struct _config cfg_t;
 
 extern cfg_t *create(const char *id);
+extern const char *error(cfg_t *c);
 extern bool   config(cfg_t *c, const char *key, const char *value);
 extern bool   append(cfg_t *c, const char *pattern);
 extern bool    ready(cfg_t *c);
diff --git a/src/filters/preg.c b/src/filters/preg.c
index 263aa46..fdaf0e9 100644
--- a/src/filters/preg.c
+++ b/src/filters/preg.c
@@ -18,6 +18,7 @@ typedef struct f2b_regex_t {
 
 struct _config {
   char id[32];
+  char error[256];
   bool icase;
   f2b_regex_t *regexps;
 };
@@ -94,6 +95,13 @@ ready(cfg_t *cfg) {
   return false;
 }
 
+const char *
+error(cfg_t *cfg) {
+  assert(cfg != NULL);
+
+  return cfg->error;
+}
+
 bool
 match(cfg_t *cfg, const char *line, char *buf, size_t buf_size) {
   f2b_regex_t *r = NULL;