diff --git a/src/stdafx.h b/src/stdafx.h
index a46b7270d8..703cc1bfdf 100644
--- a/src/stdafx.h
+++ b/src/stdafx.h
@@ -202,7 +202,7 @@
 
 #endif /* defined(_MSC_VER) */
 
-#if !defined(STRGEN) && !defined(SETTINGSGEN)
+#if !defined(STRGEN) && !defined(SETTINGSGEN) && !defined(OPENTTD_TEST)
 #	if defined(_WIN32)
 		char *getcwd(char *buf, size_t size);
 #		include <io.h>
@@ -222,7 +222,7 @@
 		template <typename T> std::string FS2OTTD(T name) { return name; }
 		template <typename T> std::string OTTD2FS(T name) { return name; }
 #	endif /* _WIN32 or WITH_ICONV */
-#endif /* STRGEN || SETTINGSGEN */
+#endif /* STRGEN || SETTINGSGEN || OPENTTD_TEST */
 
 #if defined(_WIN32)
 #	define PATHSEP "\\"
diff --git a/src/tests/bitmath_func.cpp b/src/tests/bitmath_func.cpp
index 5f5f7c79bb..dfd6365f78 100644
--- a/src/tests/bitmath_func.cpp
+++ b/src/tests/bitmath_func.cpp
@@ -7,6 +7,7 @@
 
 /** @file bitmath_func_test.cpp Test functionality from core/bitmath_func. */
 
+#define OPENTTD_TEST
 #include "../stdafx.h"
 
 #include "../3rdparty/catch2/catch.hpp"
diff --git a/src/tests/landscape_partial_pixel_z.cpp b/src/tests/landscape_partial_pixel_z.cpp
index f5c22786f7..26b7c70892 100644
--- a/src/tests/landscape_partial_pixel_z.cpp
+++ b/src/tests/landscape_partial_pixel_z.cpp
@@ -7,6 +7,7 @@
 
 /** @file landscape_partial_pixel_z.cpp Tests for consistency/validity of the results of GetPartialPixelZ. */
 
+#define OPENTTD_TEST
 #include "../stdafx.h"
 
 #include "../3rdparty/catch2/catch.hpp"
diff --git a/src/tests/math_func.cpp b/src/tests/math_func.cpp
index 45667b9012..2b2ecaf24e 100644
--- a/src/tests/math_func.cpp
+++ b/src/tests/math_func.cpp
@@ -7,6 +7,7 @@
 
 /** @file math_func_test.cpp Test functionality from core/math_func. */
 
+#define OPENTTD_TEST
 #include "../stdafx.h"
 
 #include "../3rdparty/catch2/catch.hpp"
diff --git a/src/tests/ring_buffer.cpp b/src/tests/ring_buffer.cpp
index 5075af538b..1de6ecea37 100644
--- a/src/tests/ring_buffer.cpp
+++ b/src/tests/ring_buffer.cpp
@@ -7,6 +7,7 @@
 
 /** @file ring_buffer.cpp Test functionality from core/ring_buffer.hpp */
 
+#define OPENTTD_TEST
 #include "../stdafx.h"
 
 #include "../3rdparty/catch2/catch.hpp"
diff --git a/src/tests/test_main.cpp b/src/tests/test_main.cpp
index 85649aea01..8a4d058fbc 100644
--- a/src/tests/test_main.cpp
+++ b/src/tests/test_main.cpp
@@ -7,6 +7,7 @@
 
 /** @file test_main.cpp Entry point for all the unit tests. */
 
+#define OPENTTD_TEST
 #include "../stdafx.h"
 
 #include <stdarg.h>