3 files changed, 26 insertions, 5 deletions
diff --git a/includes/stg/DLL.h b/includes/stg/DLL.h
index ec64404e62..d23002afd8 100644
--- a/includes/stg/DLL.h
+++ b/includes/stg/DLL.h
@@ -15,13 +15,22 @@
 #define __STGDLL_H__ 1
 
 #if defined(COMPILING_WINDOWS_DLL)
-#  define DLL_IMPORT_DATA_REF(x) (_imp__##x)
-#  define DLL_IMPORT_DATA_VARNAME(x) *_imp__##x
+#  if defined(x86_64_HOST_ARCH)
+#    define DLL_IMPORT_DATA_REF(x) (__imp_##x)
+#    define DLL_IMPORT_DATA_VARNAME(x) *__imp_##x
+#  else
+#    define DLL_IMPORT_DATA_REF(x) (_imp__##x)
+#    define DLL_IMPORT_DATA_VARNAME(x) *_imp__##x
+#  endif
 #  if __GNUC__ && !defined(__declspec)
 #    define DLLIMPORT
 #  else
 #    define DLLIMPORT __declspec(dllimport)
-#    define DLLIMPORT_DATA(x) _imp__##x
+#    if defined(x86_64_HOST_ARCH)
+#      define DLLIMPORT_DATA(x) __imp_##x
+#    else
+#      define DLLIMPORT_DATA(x) _imp__##x
+#    endif
 #  endif
 #else
 #  define DLL_IMPORT_DATA_REF(x) (&(x))
@@ -46,7 +55,11 @@
 #define DLL_IMPORT
 #define DLL_IMPORT_RTS DLLIMPORT
 # if defined(COMPILING_WINDOWS_DLL)
-#  define DLL_IMPORT_DATA_VAR(x) _imp__##x
+#  if defined(x86_64_HOST_ARCH)
+#   define DLL_IMPORT_DATA_VAR(x) __imp_##x
+#  else
+#   define DLL_IMPORT_DATA_VAR(x) _imp__##x
+#  endif
 # else
 #  define DLL_IMPORT_DATA_VAR(x) x
 # endif
diff --git a/rts/Linker.c b/rts/Linker.c
index 26f734c758..2899ee1a29 100644
--- a/rts/Linker.c
+++ b/rts/Linker.c
@@ -1316,7 +1316,11 @@ typedef struct _RtsSymbolVal {
 #define SymI_NeedsProto(vvv)  extern void vvv(void);
 #if defined(COMPILING_WINDOWS_DLL)
 #define SymE_HasProto(vvv)    SymE_HasProto(vvv);
-#define SymE_NeedsProto(vvv)    extern void _imp__ ## vvv (void);
+#  if defined(x86_64_HOST_ARCH)
+#    define SymE_NeedsProto(vvv)    extern void __imp_ ## vvv (void);
+#  else
+#    define SymE_NeedsProto(vvv)    extern void _imp__ ## vvv (void);
+#  endif
 #else
 #define SymE_NeedsProto(vvv)  SymI_NeedsProto(vvv);
 #define SymE_HasProto(vvv)    SymI_HasProto(vvv)
diff --git a/rts/win32/ThrIOManager.c b/rts/win32/ThrIOManager.c
index 234d4dcfe4..41a1505de0 100644
--- a/rts/win32/ThrIOManager.c
+++ b/rts/win32/ThrIOManager.c
@@ -153,7 +153,11 @@ ioManagerStart (void)
     if (io_manager_event == INVALID_HANDLE_VALUE) {
 	cap = rts_lock();
 #if defined(COMPILING_WINDOWS_DLL)
+#  if defined(x86_64_HOST_ARCH)
+        rts_evalIO(&cap,__imp_base_GHCziConcziIO_ensureIOManagerIsRunning_closure,NULL);
+#  else
         rts_evalIO(&cap,_imp__base_GHCziConcziIO_ensureIOManagerIsRunning_closure,NULL);
+#  endif
 #else
         rts_evalIO(&cap,&base_GHCziConcziIO_ensureIOManagerIsRunning_closure,NULL);
 #endif