diff --git a/platform/Makefile.am b/platform/Makefile.am
index c9fdfe0..f1a02ce 100644
--- a/platform/Makefile.am
+++ b/platform/Makefile.am
@@ -2,23 +2,28 @@ noinst_LTLIBRARIES = libplatform.la
 
 INCLUDES = -I$(top_srcdir)
 
-X = beos.cpp
-Y = beos.cpp
-
 if BUILD_BEOS_CPP
-  Y =
+    BEOS_SRC = beos.cpp
 else
-  X =
+    BEOS_SRC =
 endif
 
+if !BUILD_BEOS_CPP
+    BEOS_EXTRA = beos.cpp
+else
+    BEOS_EXTRA =
+endif
+
+
 libplatform_la_SOURCES =	\
 	unix.c                  \
 	posix.c                 \
-	$(X)
+    $(BEOS_SRC)
+
 
 EXTRA_DIST =      \
 	skeleton.c    \
 	macclassic.c  \
 	win32.c       \
-	$(Y)
+    $(BEOS_EXTRA)