diff --git a/src/system/libroot/add-ons/icu/ICUCollateData.cpp b/src/system/libroot/add-ons/icu/ICUCollateData.cpp
index ce6f8bfb7f..4943c19a0c 100644
--- a/src/system/libroot/add-ons/icu/ICUCollateData.cpp
+++ b/src/system/libroot/add-ons/icu/ICUCollateData.cpp
@@ -6,6 +6,7 @@
 
 #include "ICUCollateData.h"
 
+#include <assert.h>
 #include <string.h>
 #include <strings.h>
 #include <wchar.h>