diff --git a/src/modules/file_out/file_out.c b/src/modules/file_out/file_out.c
index 7e035f13359..886f01f944f 100644
--- a/src/modules/file_out/file_out.c
+++ b/src/modules/file_out/file_out.c
@@ -344,7 +344,7 @@ static int fo_add_filename(modparam_t type, void *val)
 		LM_ERR("modparam value is null\n");
 		return -1;
 	}
-	if(strlen((char *)val) == 0) {
+	if(strlen(((str *)val)->s) == 0) {
 		LM_ERR("modparam value is empty\n");
 		return -1;
 	}