diff --git a/build/jam/BuildSetup b/build/jam/BuildSetup
index 41b6398a01..a274c48a99 100644
--- a/build/jam/BuildSetup
+++ b/build/jam/BuildSetup
@@ -574,10 +574,9 @@ HOST_BE_API_HEADERS =
 	[ FDirName $(HAIKU_TOP) headers build os support ]
 	[ FDirName $(HAIKU_TOP) headers build private ]
 ;
-if ! $(HOST_PLATFORM_HAIKU_COMPATIBLE) {
-	HOST_BE_API_CCFLAGS = -include BeOSBuildCompatibility.h ;
-	HOST_BE_API_C++FLAGS = $(HOST_BE_API_CCFLAGS) ;
-}
+HOST_BE_API_CCFLAGS = -include [ FDirName $(HAIKU_TOP) headers build
+	BeOSBuildCompatibility.h ] ;
+HOST_BE_API_C++FLAGS = $(HOST_BE_API_CCFLAGS) ;
 
 
 #pragma mark - target platform settings
diff --git a/headers/build/os/support/Errors.h b/headers/build/os/support/Errors.h
index b7fe19d6a4..0b5306c920 100644
--- a/headers/build/os/support/Errors.h
+++ b/headers/build/os/support/Errors.h
@@ -215,12 +215,14 @@
 #define HAIKU_EPIPE			B_TO_POSIX_ERROR(B_BUSTED_PIPE)
 
 /* new error codes that can be mapped to POSIX errors */
+#ifndef BUILDING_HAIKU_ERROR_MAPPER
 #define B_BUFFER_OVERFLOW			B_FROM_POSIX_ERROR(HAIKU_EOVERFLOW)
 #define B_TOO_MANY_ARGS				B_FROM_POSIX_ERROR(HAIKU_E2BIG)
 #define B_FILE_TOO_LARGE			B_FROM_POSIX_ERROR(HAIKU_EFBIG)
 #define B_RESULT_NOT_REPRESENTABLE	B_FROM_POSIX_ERROR(HAIKU_ERANGE)
 #define B_DEVICE_NOT_FOUND			B_FROM_POSIX_ERROR(HAIKU_ENODEV)
 #define B_NOT_SUPPORTED				B_FROM_POSIX_ERROR(HAIKU_EOPNOTSUPP)
+#endif
 
 /* Media Kit Errors */
 #define B_STREAM_NOT_FOUND				(B_MEDIA_ERROR_BASE + 0)