diff --git a/rts/IOManager.c b/rts/IOManager.c
index 43474d70fb17d2116f8c71c5525913df996287a9..072aa8abd754a344d977860d254c9c461977df87 100644
--- a/rts/IOManager.c
+++ b/rts/IOManager.c
@@ -211,15 +211,30 @@ void initCapabilityIOManager(CapIOManager **piomgr)
       (CapIOManager *) stgMallocBytes(sizeof(CapIOManager),
                                       "initCapabilityIOManager");
 
-#if defined(THREADED_RTS)
-#if !defined(mingw32_HOST_OS)
-    iomgr->control_fd = -1;
+    switch (iomgr_type) {
+#if defined(IOMGR_ENABLED_SELECT)
+        case IO_MANAGER_SELECT:
+            iomgr->blocked_queue_hd = END_TSO_QUEUE;
+            iomgr->blocked_queue_tl = END_TSO_QUEUE;
+            iomgr->sleeping_queue   = END_TSO_QUEUE;
+            break;
 #endif
-#else // !defined(THREADED_RTS)
-    iomgr->blocked_queue_hd = END_TSO_QUEUE;
-    iomgr->blocked_queue_tl = END_TSO_QUEUE;
-    iomgr->sleeping_queue   = END_TSO_QUEUE;
+
+#if defined(IOMGR_ENABLED_WIN32_LEGACY)
+        case IO_MANAGER_WIN32_LEGACY:
+            iomgr->blocked_queue_hd = END_TSO_QUEUE;
+            iomgr->blocked_queue_tl = END_TSO_QUEUE;
+            break;
+#endif
+
+#if defined(IOMGR_ENABLED_MIO_POSIX)
+        case IO_MANAGER_MIO_POSIX:
+            iomgr->control_fd = -1;
+            break;
 #endif
+        default:
+            break;
+    }
 
     *piomgr = iomgr;
 }
@@ -376,12 +391,25 @@ void markCapabilityIOManager(evac_fn       evac  USED_IF_NOT_THREADS,
                              CapIOManager *iomgr USED_IF_NOT_THREADS)
 {
 
-#if !defined(THREADED_RTS)
-    evac(user, (StgClosure **)(void *)&iomgr->blocked_queue_hd);
-    evac(user, (StgClosure **)(void *)&iomgr->blocked_queue_tl);
-    evac(user, (StgClosure **)(void *)&iomgr->sleeping_queue);
+    switch (iomgr_type) {
+#if defined(IOMGR_ENABLED_SELECT)
+        case IO_MANAGER_SELECT:
+            evac(user, (StgClosure **)(void *)&iomgr->blocked_queue_hd);
+            evac(user, (StgClosure **)(void *)&iomgr->blocked_queue_tl);
+            evac(user, (StgClosure **)(void *)&iomgr->sleeping_queue);
+            break;
 #endif
 
+#if defined(IOMGR_ENABLED_WIN32_LEGACY)
+        case IO_MANAGER_WIN32_LEGACY:
+            evac(user, (StgClosure **)(void *)&iomgr->blocked_queue_hd);
+            evac(user, (StgClosure **)(void *)&iomgr->blocked_queue_tl);
+            break;
+#endif
+        default:
+            break;
+    }
+
 }
 
 
diff --git a/rts/IOManager.h b/rts/IOManager.h
index 1e34d6b16650391229216529794aa425ce7e00e0..fb25d1f7e40a2572ece294f9b88d735cee6f8f5f 100644
--- a/rts/IOManager.h
+++ b/rts/IOManager.h
@@ -190,27 +190,25 @@ bool is_io_mng_native_p (void);
  */
 typedef struct {
 
-#if defined(THREADED_RTS)
-#if !defined(mingw32_HOST_OS)
-    /* Control FD for the MIO manager for this capability */
-    int control_fd;
+#if defined(IOMGR_ENABLED_SELECT)
+    /* Thread queue for threads blocked on I/O completion. */
+    StgTSO *blocked_queue_hd;
+    StgTSO *blocked_queue_tl;
+
+    /* Thread queue for threads blocked on timeouts. */
+    StgTSO *sleeping_queue;
 #endif
-#else // !defined(THREADED_RTS)
-    /* Thread queue for threads blocked on I/O completion.
-     * Used by the select() and Win32 MIO I/O managers. It is not used by
-     * the WinIO I/O manager, though it remains defined in this case.
-     */
+
+#if defined(IOMGR_ENABLED_WIN32_LEGACY)
+    /* Thread queue for threads blocked on I/O completion. */
     StgTSO *blocked_queue_hd;
     StgTSO *blocked_queue_tl;
+#endif
 
-    /* Thread queue for threads blocked on timeouts.
-     * Used by the select() I/O manager only. It is grossly inefficient, like
-     * everything else to do with the select() I/O manager.
-     *
-     * TODO: It is not used by any of the Windows I/O managers, though it
-     * remains defined for them. This is an oddity that should be resolved.
+#if defined(IOMGR_ENABLED_MIO_POSIX)
+    /* Control FD for the (posix) MIO manager for this capability,
      */
-    StgTSO *sleeping_queue;
+    int control_fd;
 #endif
 
 } CapIOManager;