diff --git a/unittests/APITests/Allocator.cpp b/unittests/APITests/Allocator.cpp
index 9c7119d68..c1aa86d06 100644
--- a/unittests/APITests/Allocator.cpp
+++ b/unittests/APITests/Allocator.cpp
@@ -1,6 +1,8 @@
 #include <catch2/catch_all.hpp>
 #include <FEXCore/Utils/Allocator.h>
 
+#include <unistd.h>
+
 namespace {
 
 using FEXCore::Allocator::MemoryRegion;