4 files changed, 14 insertions, 12 deletions
diff --git a/include/cru/common/platform/osx/Convert.h b/include/cru/common/platform/osx/Convert.h
index 503576be..395cbbae 100644
--- a/include/cru/common/platform/osx/Convert.h
+++ b/include/cru/common/platform/osx/Convert.h
@@ -1,6 +1,9 @@
 #pragma once
 #include "../../PreConfig.h"
-#ifdef CRU_PLATFORM_OSX
+
+#ifndef CRU_PLATFORM_OSX
+#error "This file can only be included on osx."
+#endif
 
 #include "../../String.h"
 
@@ -13,5 +16,3 @@ String Convert(CFStringRef string);
 CFRange Convert(const Range& range);
 Range Convert(const CFRange& range);
 }  // namespace cru::platform::osx
-
-#endif
diff --git a/include/cru/common/platform/osx/Exception.h b/include/cru/common/platform/osx/Exception.h
index 53e874e9..5ab14ebd 100644
--- a/include/cru/common/platform/osx/Exception.h
+++ b/include/cru/common/platform/osx/Exception.h
@@ -1,6 +1,9 @@
 #pragma once
 #include "../../PreConfig.h"
-#ifdef CRU_PLATFORM_OSX
+
+#ifndef CRU_PLATFORM_OSX
+#error "This file can only be included on osx."
+#endif
 
 #include "../Exception.h"
 
@@ -10,5 +13,3 @@ class OsxException : public PlatformException {
   using PlatformException::PlatformException;
 };
 }  // namespace cru::platform::osx
-
-#endif
diff --git a/include/cru/common/platform/unix/UnixFileStream.h b/include/cru/common/platform/unix/UnixFileStream.h
index 06b45d08..43615776 100644
--- a/include/cru/common/platform/unix/UnixFileStream.h
+++ b/include/cru/common/platform/unix/UnixFileStream.h
@@ -2,7 +2,9 @@
 
 #include "../../PreConfig.h"
 
-#ifdef CRU_PLATFORM_UNIX
+#ifndef CRU_PLATFORM_UNIX
+#error "This file can only be included on unix."
+#endif
 
 #include "../../io/Stream.h"
 
@@ -48,5 +50,3 @@ class UnixFileStream : public io::Stream {
   bool auto_close_;
 };
 }  // namespace cru::platform::unix
-
-#endif
diff --git a/include/cru/common/platform/unix/UnixPipe.h b/include/cru/common/platform/unix/UnixPipe.h
index 2ea80bde..afe6024a 100644
--- a/include/cru/common/platform/unix/UnixPipe.h
+++ b/include/cru/common/platform/unix/UnixPipe.h
@@ -2,7 +2,9 @@
 
 #include "../../PreConfig.h"
 
-#ifdef CRU_PLATFORM_UNIX
+#ifndef CRU_PLATFORM_UNIX
+#error "This file can only be included on unix."
+#endif
 
 #include "../../Base.h"
 #include "../../Bitmask.h"
@@ -65,5 +67,3 @@ class UnixPipe : public Object {
   int write_fd_;
 };
 }  // namespace cru::platform::unix
-
-#endif