diff --git a/sim/mcuboot-sys/build.rs b/sim/mcuboot-sys/build.rs
index 516741b..81e21d1 100644
--- a/sim/mcuboot-sys/build.rs
+++ b/sim/mcuboot-sys/build.rs
@@ -17,6 +17,7 @@
     let mut conf = gcc::Build::new();
     conf.define("__BOOTSIM__", None);
     conf.define("MCUBOOT_USE_FLASH_AREA_GET_SECTORS", None);
+    conf.define("MCUBOOT_HAVE_ASSERT_H", None);
     conf.define("MCUBOOT_MAX_IMG_SECTORS", Some("128"));
 
     if validate_slot0 {