diff --git a/setup.py b/setup.py
index d05c050..7810d42 100644
--- a/setup.py
+++ b/setup.py
@@ -13,10 +13,11 @@
 
 machine = platform.machine().lower()
 IS_X86 = machine in ['i386', 'i686', 'x86_64', 'amd64']
-IS_X86_64 = machine in ['x86_64']
+IS_X86_64 = IS_X86 and IS_64BITS
 IS_ARM = machine.startswith('arm') or machine.startswith('aarch')
 IS_ARM64 = IS_ARM and IS_64BITS
 IS_PPC = machine.startswith('ppc')
+IS_PPC64 = IS_PPC and IS_64BITS
 
 IS_WINNT = os.name == "nt"
 IS_POSIX = os.name == "posix"
@@ -198,7 +199,7 @@ def cpu_features():
             '-mfpu=neon',
         ]
 
-    elif IS_PPC:
+    elif IS_PPC64:
         srcs += ["src/highwayhash/highwayhash/hh_vsx.cc"]
         cflags += ['-mvsx']