diff --git a/cdr.c b/cdr.c
index f00fdac..786c504 100644
--- a/cdr.c
+++ b/cdr.c
@@ -1711,3 +1711,20 @@ void cdr_truncate_call_id_suffix(char *callid)
         break;
     };
 }
+
+static bool cdr_verify_field(const GString *f, size_t max) {
+	return !(max && f->len > max);
+}
+
+// return false if one of the fields is too long
+bool cdr_verify_fields(const cdr_entry_t *cdr) {
+#define F(f, x) if (cdr_verify_field(cdr->f, x)) return false;
+#define FA(f, a, x) for (unsigned int j = 0; j < a; j++) if (cdr_verify_field(cdr->f[j], x)) return false;
+
+#include "cdr_field_names.inc"
+
+#undef F
+#undef FA
+
+	return true;
+}
diff --git a/cdr.h b/cdr.h
index 4db9e1e..085404b 100644
--- a/cdr.h
+++ b/cdr.h
@@ -2,6 +2,7 @@
 #define _CDR_H
 
 #include "mediator.h"
+#include <stdbool.h>
 
 #define MSG_INVITE "INVITE"
 #define MSG_BYE    "BYE"
@@ -64,6 +65,7 @@ int cdr_process_records(GQueue *records, uint64_t *cdr_count, struct medmysql_ba
         int do_intermediate);
 void cdr_parse_entry(med_entry_t *);
 void cdr_truncate_call_id_suffix(char *);
+bool cdr_verify_fields(const cdr_entry_t *);
 
 
 #endif /* _CDR_H */
diff --git a/medmysql.c b/medmysql.c
index 7ec484b..81136d8 100644
--- a/medmysql.c
+++ b/medmysql.c
@@ -1100,7 +1100,15 @@ int medmysql_insert_cdrs(cdr_entry_t *entries, uint64_t count, struct medmysql_b
         CDRPRINT("),");
 
 	const char *end_ptr = batch->cdrs.str + batch->cdrs.len;
-	L_DEBUG("CDR entry to be written: %.*s", (int) (end_ptr - begin_ptr), begin_ptr);
+	size_t cdr_len = end_ptr - begin_ptr;
+	L_DEBUG("CDR entry to be written: %.*s", (int) cdr_len, begin_ptr);
+
+	if (!cdr_verify_fields(e)) {
+		L_WARNING("CDR field verification failed for record");
+		// backtrack
+		batch->cdrs.len -= cdr_len;
+		continue;
+	}
 
         single_cdr *single = g_slice_alloc(sizeof(*single));
         single->begin = begin_ptr;
@@ -1758,7 +1766,7 @@ static int medmysql_flush_cdr_batch(struct medmysql_cdr_batch *batch) {
         fclose(qlog);
     }
 
-    if (!batch->cdrs.len)
+    if (!batch->num_cdrs)
         return 0;