diff --git a/src/database.c b/src/database.c
index 0482634..8ccb6dd 100644
--- a/src/database.c
+++ b/src/database.c
@@ -170,6 +170,8 @@ simdb_error(int error) {
     return "database opened in read-only mode";
   } else if (error == SIMDB_ERR_NXRECORD) {
     return "no such record in database";
+  } else if (error == SIMDB_ERR_USAGE) {
+    return "wrong parameters passed to finction";
   }
   return "unknown error";
 }
diff --git a/src/simdb.h b/src/simdb.h
index 63cf57f..6602ec4 100644
--- a/src/simdb.h
+++ b/src/simdb.h
@@ -34,6 +34,7 @@
 #define SIMDB_ERR_WRONGVERS   -4 /**< database version mismatch */
 #define SIMDB_ERR_NXRECORD    -5 /**< no such record in database */
 #define SIMDB_ERR_READONLY    -6 /**< database opened in read-only mode */
+#define SIMDB_ERR_USAGE       -7 /**< wrong arguments passed */
 /** @} */
 
 /** opaque database handler */