diff --git a/BUILDING.txt b/BUILDING.txt
index 8634e3dc..15155184 100644
--- a/BUILDING.txt
+++ b/BUILDING.txt
@@ -275,14 +275,10 @@ This will generate the following files under libjpeg-turbo\windows\:
   turbojpeg.dll          Shared library for TurboJPEG/OSS
   turbojpeg.lib          Development stub for TurboJPEG/OSS shared library
 
-#If a 64-bit Windows platform is detected, then the build system will attempt
-#to build a 64-bit version of libjpeg-turbo.  You can override this by running
-#
-#  make -f win/Makefile WIN64=no
+If a 64-bit Windows platform is detected, then the build system will attempt
+to build a 64-bit version of libjpeg-turbo.  You can override this by running
 
-NOTE:  For unknown reasons, Win64 support doesn't work yet, so at the moment,
-you have to run 'make -f win/Makefile WIN64=yes' to get a 64-bit build on
-64-bit Windows.  The paragraph above will apply once Win64 support is working.
+  make -f win/Makefile WIN64=no
 
 
 *******************************************************************************
diff --git a/simd/jsimdext.inc b/simd/jsimdext.inc
index d0b47e63..54dba9ad 100644
--- a/simd/jsimdext.inc
+++ b/simd/jsimdext.inc
@@ -310,6 +310,19 @@ const_base:
 	mov r13, r9
 	mov r14, [rax+48]
 	mov r15, [rax+56]
+	push rsi
+	push rdi
+%endmacro
+
+%imacro uncollect_args 0
+	pop rdi
+	pop rsi
+	pop r15
+	pop r14
+	pop r13
+	pop r12
+	pop r11
+	pop r10
 %endmacro
 
 %else
@@ -329,8 +342,6 @@ const_base:
 	mov r15, r9
 %endmacro
 
-%endif
-
 %imacro uncollect_args 0
 	pop r15
 	pop r14
@@ -342,6 +353,8 @@ const_base:
 
 %endif
 
+%endif
+
 ; --------------------------------------------------------------------------
 ;  Defines picked up from the C headers
 ;
diff --git a/win/Makerules b/win/Makerules
index 3850c22b..8aa258a6 100755
--- a/win/Makerules
+++ b/win/Makerules
@@ -1,13 +1,12 @@
 ODIR = windows
 WIN64 = no
-# Win64 doesn't work yet, for unknown reasons
-#ifeq ($(PROCESSOR_ARCHITECTURE), AMD64)
-# WIN64 = yes
-#else
-# ifeq ($(PROCESSOR_ARCHITEW6432), AMD64)
-#  WIN64 = yes
-# endif
-#endif
+ifeq ($(PROCESSOR_ARCHITECTURE), AMD64)
+ WIN64 = yes
+else
+ ifeq ($(PROCESSOR_ARCHITEW6432), AMD64)
+  WIN64 = yes
+ endif
+endif
 ifeq ($(WIN64), yes)
 ODIR = windows64
 endif