diff --git a/libs/backends/jack/weak_libjack.c b/libs/backends/jack/weak_libjack.c
index 775410287b..885ca60f54 100644
--- a/libs/backends/jack/weak_libjack.c
+++ b/libs/backends/jack/weak_libjack.c
@@ -110,7 +110,7 @@ static void init_weak_jack(void)
 		lib = lib_open("/usr/local/lib/libjack.dylib");
 	}
 #elif (defined PLATFORM_WINDOWS)
-# ifdef __x86_64__
+# if ( defined(__x86_64__) || defined(_M_X64) )
 	lib = lib_open("libjack64.dll");
 # else
 	lib = lib_open("libjack.dll");
diff --git a/libs/pbd/fpu.cc b/libs/pbd/fpu.cc
index 76de065d28..92c6d3e41a 100644
--- a/libs/pbd/fpu.cc
+++ b/libs/pbd/fpu.cc
@@ -43,7 +43,7 @@ FPU::FPU ()
 
 	_flags = Flags (0);
 
-#if !( (defined __x86_64__) || (defined __i386__) ) // !ARCH_X86
+#if !( (defined __x86_64__) || (defined __i386__) || (defined _M_X64) || (defined _M_IX86) ) // !ARCH_X86
 	return;
 #else
 
diff --git a/libs/pbd/malign.cc b/libs/pbd/malign.cc
index 978ca00451..a11a23f35f 100644
--- a/libs/pbd/malign.cc
+++ b/libs/pbd/malign.cc
@@ -29,7 +29,7 @@
 
 using namespace PBD;
 
-#ifdef __x86_64__
+#if ( defined(__x86_64__) || defined(_M_X64) )
 static const int CPU_CACHE_ALIGN = 64;
 #else
 static const int CPU_CACHE_ALIGN = 16; /* arguably 32 on most arches, but it matters less */