diff --git a/msvc/Makefile b/msvc/Makefile
index d6fe218e7..74fde1ac4 100755
--- a/msvc/Makefile
+++ b/msvc/Makefile
@@ -87,10 +87,10 @@ CFLAGS_SSE=/arch:SSE2
 
 !if "$(ECL_WIN64)" != ""
 GMP_BITS=64
-GC_CPU=AMD64
+GC_CPU=X64
 !else
 GMP_BITS=32
-GC_CPU=X86
+GC_CPU=i386
 !endif
 
 #
diff --git a/msvc/gc/Makefile b/msvc/gc/Makefile
index d16ec5052..8de54736a 100644
--- a/msvc/gc/Makefile
+++ b/msvc/gc/Makefile
@@ -44,7 +44,7 @@ all: gc.lib
 $(OBJS) tests\test.obj: $(srcdir)\include\private\gc_priv.h $(srcdir)\include\private\gc_hdrs.h $(srcdir)\include\gc.h $(srcdir)\include\private\gcconfig.h $(srcdir)\include\private\gc_locks.h $(srcdir)\include\private\gc_pmark.h $(srcdir)\include\gc_mark.h $(srcdir)\include\private\msvc_dbg.h
 
 gc.lib: $(OBJS)
-!if "$(CPU)" == "X386"
+!if "$(CPU)" == "i386"
 	lib /MACHINE:i386 /out:gc.lib $(OBJS)
 !else
 	lib /MACHINE:X64 /out:gc.lib $(OBJS)