diff --git a/src/core/internal/abort.d b/src/core/internal/abort.d
index 07f04ee660..05733b5fd9 100644
--- a/src/core/internal/abort.d
+++ b/src/core/internal/abort.d
@@ -19,7 +19,7 @@ void abort(scope string msg, scope string filename = __FILE__, size_t line = __L
     }
     else version (Windows)
     {
-        import core.sys.windows.windows: GetStdHandle, STD_ERROR_HANDLE, WriteFile, INVALID_HANDLE_VALUE;
+        import core.sys.windows.winbase : GetStdHandle, STD_ERROR_HANDLE, WriteFile, INVALID_HANDLE_VALUE;
         auto h = (() @trusted => GetStdHandle(STD_ERROR_HANDLE))();
         if (h == INVALID_HANDLE_VALUE)
             // attempt best we can to print the message
diff --git a/src/core/runtime.d b/src/core/runtime.d
index a77f0edbc0..283c47c7bf 100644
--- a/src/core/runtime.d
+++ b/src/core/runtime.d
@@ -227,7 +227,8 @@ struct Runtime
         import core.stdc.stdlib : free, malloc;
         version (Windows)
         {
-            import core.sys.windows.windows;
+            import core.sys.windows.winnls : CP_UTF8, MultiByteToWideChar;
+            import core.sys.windows.winnt : WCHAR;
 
             if (name.length == 0) return null;
             // Load a DLL at runtime
@@ -990,7 +991,7 @@ Throwable.TraceInfo defaultTraceHandler( void* ptr = null )
         {
             static enum FIRSTFRAME = 0;
         }
-        import core.sys.windows.windows : CONTEXT;
+        import core.sys.windows.winnt : CONTEXT;
         auto s = new StackTrace(FIRSTFRAME, cast(CONTEXT*)ptr);
         return s;
     }
diff --git a/src/core/sync/condition.d b/src/core/sync/condition.d
index 30f990cf30..18f5ff3161 100644
--- a/src/core/sync/condition.d
+++ b/src/core/sync/condition.d
@@ -23,7 +23,12 @@ public import core.time;
 version (Windows)
 {
     private import core.sync.semaphore;
-    private import core.sys.windows.windows;
+    private import core.sys.windows.basetsd /+: HANDLE+/;
+    private import core.sys.windows.winbase /+: CloseHandle, CreateSemaphoreA, CRITICAL_SECTION,
+        DeleteCriticalSection, EnterCriticalSection, INFINITE, InitializeCriticalSection,
+        LeaveCriticalSection, ReleaseSemaphore, WAIT_OBJECT_0, WaitForSingleObject+/;
+    private import core.sys.windows.windef /+: BOOL, DWORD+/;
+    private import core.sys.windows.winerror /+: WAIT_TIMEOUT+/;
 }
 else version (Posix)
 {
diff --git a/src/core/sync/mutex.d b/src/core/sync/mutex.d
index c026c1421a..67c9f18d46 100644
--- a/src/core/sync/mutex.d
+++ b/src/core/sync/mutex.d
@@ -20,7 +20,9 @@ public import core.sync.exception;
 
 version (Windows)
 {
-    private import core.sys.windows.windows;
+    private import core.sys.windows.winbase /+: CRITICAL_SECTION, DeleteCriticalSection,
+        EnterCriticalSection, InitializeCriticalSection, LeaveCriticalSection,
+        TryEnterCriticalSection+/;
 }
 else version (Posix)
 {
diff --git a/src/core/sync/semaphore.d b/src/core/sync/semaphore.d
index c1c9034789..a7e52fa9d8 100644
--- a/src/core/sync/semaphore.d
+++ b/src/core/sync/semaphore.d
@@ -29,7 +29,11 @@ else version (WatchOS)
 
 version (Windows)
 {
-    private import core.sys.windows.windows;
+    private import core.sys.windows.basetsd /+: HANDLE+/;
+    private import core.sys.windows.winbase /+: CloseHandle, CreateSemaphoreA, INFINITE,
+        ReleaseSemaphore, WAIT_OBJECT_0, WaitForSingleObject+/;
+    private import core.sys.windows.windef /+: BOOL, DWORD+/;
+    private import core.sys.windows.winerror /+: WAIT_TIMEOUT+/;
 }
 else version (Darwin)
 {
diff --git a/src/core/sys/windows/aclapi.d b/src/core/sys/windows/aclapi.d
index ed05161bb0..762a4dbed0 100644
--- a/src/core/sys/windows/aclapi.d
+++ b/src/core/sys/windows/aclapi.d
@@ -13,7 +13,7 @@ version (Windows):
 version (ANSI) {} else version = Unicode;
 pragma(lib, "advapi32");
 
-import core.sys.windows.windows, core.sys.windows.accctrl;
+import core.sys.windows.accctrl, core.sys.windows.basetyps, core.sys.windows.w32api, core.sys.windows.winnt;
 
 extern (Windows) {
     VOID BuildExplicitAccessWithNameA(PEXPLICIT_ACCESS_A, LPSTR, DWORD,
diff --git a/src/core/sys/windows/com.d b/src/core/sys/windows/com.d
index 15b3d9db07..34aeccc946 100644
--- a/src/core/sys/windows/com.d
+++ b/src/core/sys/windows/com.d
@@ -4,7 +4,7 @@ version (Windows):
 pragma(lib,"uuid");
 
 import core.atomic;
-import core.sys.windows.windows;
+import core.sys.windows.windef /+: HRESULT, LONG, ULONG+/;
 //import std.string;
 
 public import core.sys.windows.basetyps : GUID, IID, CLSID;
diff --git a/src/core/sys/windows/comcat.d b/src/core/sys/windows/comcat.d
index 36c6a9125c..baa0606bae 100644
--- a/src/core/sys/windows/comcat.d
+++ b/src/core/sys/windows/comcat.d
@@ -10,7 +10,7 @@
 module core.sys.windows.comcat;
 version (Windows):
 
-import core.sys.windows.windows, core.sys.windows.ole2;
+import core.sys.windows.ole2;
 private import core.sys.windows.basetyps, core.sys.windows.cguid, core.sys.windows.objbase, core.sys.windows.unknwn,
   core.sys.windows.windef, core.sys.windows.wtypes;
 
diff --git a/src/core/sys/windows/dbghelp.d b/src/core/sys/windows/dbghelp.d
index fddfc633c3..44c1957143 100644
--- a/src/core/sys/windows/dbghelp.d
+++ b/src/core/sys/windows/dbghelp.d
@@ -12,7 +12,8 @@
 module core.sys.windows.dbghelp;
 version (Windows):
 
-import core.sys.windows.windows;
+import core.sys.windows.winbase /+: FreeLibrary, GetProcAddress, LoadLibraryA+/;
+import core.sys.windows.windef;
 
 public import core.sys.windows.dbghelp_types;
 
diff --git a/src/core/sys/windows/dbghelp_types.d b/src/core/sys/windows/dbghelp_types.d
index ff52c565e1..c645cbfc01 100644
--- a/src/core/sys/windows/dbghelp_types.d
+++ b/src/core/sys/windows/dbghelp_types.d
@@ -14,7 +14,8 @@ version (Windows):
 
 version (ANSI) {} else version = Unicode;
 
-import core.sys.windows.windows;
+import core.sys.windows.windef;
+import core.sys.windows.imagehlp /+: ADDRESS_MODE+/;
 
 public import core.sys.windows.winnt : TCHAR;
 
diff --git a/src/core/sys/windows/dll.d b/src/core/sys/windows/dll.d
index 58cf4ad262..e8e0c89d0e 100644
--- a/src/core/sys/windows/dll.d
+++ b/src/core/sys/windows/dll.d
@@ -12,7 +12,8 @@
 module core.sys.windows.dll;
 version (Windows):
 
-import core.sys.windows.windows;
+import core.sys.windows.winbase;
+import core.sys.windows.winnt;
 import core.stdc.string;
 import core.runtime;
 
@@ -473,12 +474,12 @@ bool dll_thread_detach( bool detach_thread = true, bool exitTls = true )
 /// ---
 mixin template SimpleDllMain()
 {
-    import core.sys.windows.windows : HINSTANCE;
+    import core.sys.windows.windef : HINSTANCE;
 
     extern(Windows)
     bool DllMain(HINSTANCE hInstance, uint ulReason, void* reserved)
     {
-        import core.sys.windows.windows;
+        import core.sys.windows.winnt;
         import core.sys.windows.dll :
             dll_process_attach, dll_process_detach,
             dll_thread_attach, dll_thread_detach;
diff --git a/src/core/sys/windows/httpext.d b/src/core/sys/windows/httpext.d
index 93b03f58f1..9073777b02 100644
--- a/src/core/sys/windows/httpext.d
+++ b/src/core/sys/windows/httpext.d
@@ -19,7 +19,9 @@ version (Windows):
        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 */
 
-private import core.sys.windows.windows;
+private import core.sys.windows.basetsd /+: DECLARE_HANDLE, HANDLE+/;
+private import core.sys.windows.windef /+: BOOL, CHAR, DWORD, LPBYTE, LPDWORD+/;
+private import core.sys.windows.winnt /+: LPCSTR, LPSTR, LPVOID, PVOID, VOID+/;
 
 enum {
     HSE_VERSION_MAJOR               = 2,
diff --git a/src/core/sys/windows/oledlg.d b/src/core/sys/windows/oledlg.d
index 71b5dcd7c0..e44fb7dbad 100644
--- a/src/core/sys/windows/oledlg.d
+++ b/src/core/sys/windows/oledlg.d
@@ -11,8 +11,7 @@ version (Windows):
 
 version (ANSI) {} else version = Unicode;
 
-import core.sys.windows.commdlg, core.sys.windows.dlgs, core.sys.windows.ole2, core.sys.windows.prsht, core.sys.windows.shellapi,
-  core.sys.windows.windows;
+import core.sys.windows.commdlg, core.sys.windows.dlgs, core.sys.windows.ole2, core.sys.windows.prsht, core.sys.windows.shellapi;
 private import core.sys.windows.winbase, core.sys.windows.objidl, core.sys.windows.objfwd, core.sys.windows.winnt;
 
 // FIXME: remove inherited methods from interface definitions
diff --git a/src/core/sys/windows/snmp.d b/src/core/sys/windows/snmp.d
index 09901507f9..4f550184d0 100644
--- a/src/core/sys/windows/snmp.d
+++ b/src/core/sys/windows/snmp.d
@@ -10,7 +10,9 @@
 module core.sys.windows.snmp;
 version (Windows):
 
-private import core.sys.windows.windows;
+private import core.sys.windows.basetsd /+: HANDLE+/;
+private import core.sys.windows.windef /+: BOOL, BYTE, DWORD, INT, LONG, UINT, ULONG+/;
+private import core.sys.windows.winnt /+: LPSTR, LPVOID, ULARGE_INTEGER, VOID+/;
 
 // These are not documented on MSDN
 enum {
diff --git a/src/core/sys/windows/stacktrace.d b/src/core/sys/windows/stacktrace.d
index 13f33edc3e..2f817957e3 100644
--- a/src/core/sys/windows/stacktrace.d
+++ b/src/core/sys/windows/stacktrace.d
@@ -17,7 +17,9 @@ import core.runtime;
 import core.stdc.stdlib;
 import core.stdc.string;
 import core.sys.windows.dbghelp;
-import core.sys.windows.windows;
+import core.sys.windows.imagehlp /+: ADDRESS_MODE+/;
+import core.sys.windows.winbase;
+import core.sys.windows.windef;
 
 //debug=PRINTF;
 debug(PRINTF) import core.stdc.stdio;
diff --git a/src/core/sys/windows/threadaux.d b/src/core/sys/windows/threadaux.d
index df91be0c05..94ff46d325 100644
--- a/src/core/sys/windows/threadaux.d
+++ b/src/core/sys/windows/threadaux.d
@@ -12,7 +12,10 @@
 module core.sys.windows.threadaux;
 version (Windows):
 
-import core.sys.windows.windows;
+import core.sys.windows.basetsd/+ : HANDLE+/;
+import core.sys.windows.winbase/+ : CloseHandle, GetCurrentThreadId, GetCurrentProcessId,
+    GetModuleHandleA, GetProcAddress+/;
+import core.sys.windows.windef/+ : BOOL, DWORD, FALSE, HRESULT+/;
 import core.stdc.stdlib;
 
 public import core.thread;
diff --git a/src/core/sys/windows/wininet.d b/src/core/sys/windows/wininet.d
index 0528f9fbf3..296627e8e3 100644
--- a/src/core/sys/windows/wininet.d
+++ b/src/core/sys/windows/wininet.d
@@ -15,7 +15,7 @@ pragma(lib, "wininet");
 
 // FIXME: check types and grouping of constants
 
-import core.sys.windows.windows;
+import core.sys.windows.winbase, core.sys.windows.windef;
 
 enum {
     INTERNET_INVALID_PORT_NUMBER =    0,
diff --git a/src/core/thread.d b/src/core/thread.d
index f402d0939a..b75b232f94 100644
--- a/src/core/thread.d
+++ b/src/core/thread.d
@@ -65,7 +65,7 @@ version (Posix)
 }
 else version (Windows)
 {
-    alias getpid = core.sys.windows.windows.GetCurrentProcessId;
+    alias getpid = core.sys.windows.winbase.GetCurrentProcessId;
 }
 
 
@@ -185,8 +185,15 @@ version (Windows)
     {
         import core.stdc.stdint : uintptr_t; // for _beginthreadex decl below
         import core.stdc.stdlib;             // for malloc, atexit
-        import core.sys.windows.windows;
-        import core.sys.windows.threadaux;   // for OpenThreadHandle
+        import core.sys.windows.basetsd /+: HANDLE+/;
+        import core.sys.windows.threadaux /+: getThreadStackBottom, impersonate_thread, OpenThreadHandle+/;
+        import core.sys.windows.winbase /+: CloseHandle, CREATE_SUSPENDED, DuplicateHandle, GetCurrentThread,
+            GetCurrentThreadId, GetCurrentProcess, GetExitCodeThread, GetSystemInfo, GetThreadContext,
+            GetThreadPriority, INFINITE, ResumeThread, SetThreadPriority, Sleep,  STILL_ACTIVE,
+            SuspendThread, SwitchToThread, SYSTEM_INFO, THREAD_PRIORITY_IDLE, THREAD_PRIORITY_NORMAL,
+            THREAD_PRIORITY_TIME_CRITICAL, WAIT_OBJECT_0, WaitForSingleObject+/;
+        import core.sys.windows.windef /+: TRUE+/;
+        import core.sys.windows.winnt /+: CONTEXT, CONTEXT_CONTROL, CONTEXT_INTEGER+/;
 
         extern (Windows) alias btex_fptr = uint function(void*);
         extern (C) uintptr_t _beginthreadex(void*, uint, btex_fptr, void*, uint, uint*) nothrow;
diff --git a/src/core/time.d b/src/core/time.d
index 75724dac4a..d08bc0d916 100644
--- a/src/core/time.d
+++ b/src/core/time.d
@@ -85,7 +85,7 @@ import core.internal.string;
 
 version (Windows)
 {
-import core.sys.windows.windows;
+import core.sys.windows.winbase /+: QueryPerformanceCounter, QueryPerformanceFrequency+/;
 }
 else version (Posix)
 {
diff --git a/src/gc/os.d b/src/gc/os.d
index 2bff6e501f..085067d1be 100644
--- a/src/gc/os.d
+++ b/src/gc/os.d
@@ -16,7 +16,8 @@ module gc.os;
 
 version (Windows)
 {
-    import core.sys.windows.windows;
+    import core.sys.windows.winbase : GetCurrentThreadId, VirtualAlloc, VirtualFree;
+    import core.sys.windows.winnt : MEM_COMMIT, MEM_RELEASE, MEM_RESERVE, PAGE_READWRITE;
 
     alias int pthread_t;
 
@@ -172,7 +173,7 @@ version (Windows)
             return false;
         else
         {
-            import core.sys.windows.windows;
+            import core.sys.windows.winbase : GlobalMemoryStatus, MEMORYSTATUS;
             MEMORYSTATUS stat;
             GlobalMemoryStatus(&stat);
             // Less than 5 % of virtual address space available
diff --git a/src/rt/cover.d b/src/rt/cover.d
index 9e25285bb3..291a3e6a65 100644
--- a/src/rt/cover.d
+++ b/src/rt/cover.d
@@ -14,7 +14,10 @@ module rt.cover;
 private
 {
     version (Windows)
-        import core.sys.windows.windows;
+    {
+        import core.sys.windows.basetsd /+: HANDLE+/;
+        import core.sys.windows.winbase /+: LOCKFILE_EXCLUSIVE_LOCK, LockFileEx, OVERLAPPED, SetEndOfFile+/;
+    }
     else version (Posix)
     {
         import core.sys.posix.fcntl;
diff --git a/src/rt/deh_win32.d b/src/rt/deh_win32.d
index f84d83ac04..82361bb7e4 100644
--- a/src/rt/deh_win32.d
+++ b/src/rt/deh_win32.d
@@ -13,7 +13,9 @@ module rt.deh_win32;
 
 version (Win32):
 
-import core.sys.windows.windows;
+import core.sys.windows.basetsd /+: ULONG_PTR+/;
+import core.sys.windows.windef /+: BOOL, BYTE, DWORD+/;
+import core.sys.windows.winnt /+: PVOID+/;
 import rt.monitor_;
 //import core.stdc.stdio;
 
diff --git a/src/rt/dmain2.d b/src/rt/dmain2.d
index 3057ec2090..901b959589 100644
--- a/src/rt/dmain2.d
+++ b/src/rt/dmain2.d
@@ -26,7 +26,14 @@ private
 version (Windows)
 {
     private import core.stdc.wchar_;
-    private import core.sys.windows.windows;
+    private import core.sys.windows.basetsd /+: HANDLE+/;
+    private import core.sys.windows.shellapi /+: CommandLineToArgvW+/;
+    private import core.sys.windows.winbase /+: FreeLibrary, GetCommandLineW, GetProcAddress,
+        IsDebuggerPresent, LoadLibraryA, LoadLibraryW, LocalFree, WriteFile+/;
+    private import core.sys.windows.wincon /+: CONSOLE_SCREEN_BUFFER_INFO, GetConsoleOutputCP, GetConsoleScreenBufferInfo+/;
+    private import core.sys.windows.winnls /+: CP_UTF8, MultiByteToWideChar, WideCharToMultiByte+/;
+    private import core.sys.windows.winnt /+: WCHAR+/;
+    private import core.sys.windows.winuser /+: MB_ICONERROR, MessageBoxW+/;
 
     pragma(lib, "shell32.lib"); // needed for CommandLineToArgvW
 }
diff --git a/src/rt/monitor_.d b/src/rt/monitor_.d
index c9e5964461..2a9f7ee093 100644
--- a/src/rt/monitor_.d
+++ b/src/rt/monitor_.d
@@ -180,7 +180,8 @@ version (Windows)
     {
         pragma(lib, "snn.lib");
     }
-    import core.sys.windows.windows;
+    import core.sys.windows.winbase /+: CRITICAL_SECTION, DeleteCriticalSection,
+        EnterCriticalSection, InitializeCriticalSection, LeaveCriticalSection+/;
 
     alias Mutex = CRITICAL_SECTION;