diff --git a/src/afd.c b/src/afd.c
index 8d533e7..abc3336 100644
--- a/src/afd.c
+++ b/src/afd.c
@@ -1,12 +1,11 @@
-#include <malloc.h>
+#include <assert.h>
+#include <stdint.h>
 #include <stdlib.h>
 
 #include "afd.h"
 #include "error.h"
 #include "nt.h"
-#include "util.h"
 #include "win.h"
-#include "ws.h"
 
 #define IOCTL_AFD_POLL 0x00012024
 
diff --git a/src/afd.h b/src/afd.h
index c26cb8f..cc49a44 100644
--- a/src/afd.h
+++ b/src/afd.h
@@ -3,7 +3,6 @@
 
 #include "internal.h"
 #include "nt.h"
-#include "util.h"
 #include "win.h"
 
 /* clang-format off */
diff --git a/src/api.c b/src/api.c
index f330181..38513c9 100644
--- a/src/api.c
+++ b/src/api.c
@@ -6,7 +6,6 @@
 #include "init.h"
 #include "port.h"
 #include "thread-safe-tree.h"
-#include "util.h"
 #include "wepoll.h"
 #include "win.h"
 
diff --git a/src/init.c b/src/init.c
index db237d4..04f72bc 100644
--- a/src/init.c
+++ b/src/init.c
@@ -1,11 +1,12 @@
 #include <stdbool.h>
+#include <stdlib.h>
 
-#include "afd.h"
 #include "api.h"
 #include "init.h"
 #include "nt.h"
 #include "reflock.h"
 #include "util.h"
+#include "win.h"
 #include "ws.h"
 
 static bool init__done = false;
diff --git a/src/poll-group.c b/src/poll-group.c
index 442c73a..e3ded8d 100644
--- a/src/poll-group.c
+++ b/src/poll-group.c
@@ -1,7 +1,8 @@
 #include <assert.h>
-#include <malloc.h>
+#include <stdlib.h>
 #include <string.h>
 
+#include "afd.h"
 #include "error.h"
 #include "poll-group.h"
 #include "port.h"
diff --git a/src/poll-group.h b/src/poll-group.h
index 2e5cd09..2dd100d 100644
--- a/src/poll-group.h
+++ b/src/poll-group.h
@@ -1,13 +1,12 @@
 #ifndef WEPOLL_POLL_GROUP_H_
 #define WEPOLL_POLL_GROUP_H_
 
-#include "error.h"
 #include "internal.h"
-#include "queue.h"
 #include "win.h"
 
-typedef struct port_state port_state_t;
 typedef struct poll_group poll_group_t;
+typedef struct port_state port_state_t;
+typedef struct queue_node queue_node_t;
 
 WEPOLL_INTERNAL poll_group_t* poll_group_acquire(port_state_t* port);
 WEPOLL_INTERNAL void poll_group_release(poll_group_t* poll_group);
diff --git a/src/port.c b/src/port.c
index 6c8727d..c4c9241 100644
--- a/src/port.c
+++ b/src/port.c
@@ -1,5 +1,5 @@
 #include <assert.h>
-#include <malloc.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/src/port.h b/src/port.h
index d7b9215..bedfaf3 100644
--- a/src/port.h
+++ b/src/port.h
@@ -1,18 +1,14 @@
 #ifndef WEPOLL_PORT_H_
 #define WEPOLL_PORT_H_
 
-#include "afd.h"
 #include "internal.h"
-#include "poll-group.h"
-#include "queue.h"
-#include "sock.h"
-#include "thread-safe-tree.h"
-#include "tree.h"
-#include "util.h"
+#include "wepoll.h"
 #include "win.h"
 
 typedef struct port_state port_state_t;
+typedef struct queue queue_t;
 typedef struct sock_state sock_state_t;
+typedef struct ts_tree_node ts_tree_node_t;
 
 WEPOLL_INTERNAL port_state_t* port_new(HANDLE* iocp_handle_out);
 WEPOLL_INTERNAL int port_close(port_state_t* port_state);
diff --git a/src/reflock.c b/src/reflock.c
index 773e97d..98c73ca 100644
--- a/src/reflock.c
+++ b/src/reflock.c
@@ -1,5 +1,4 @@
 #include <assert.h>
-#include <stdint.h>
 #include <stdlib.h>
 
 #include "error.h"
diff --git a/src/reflock.h b/src/reflock.h
index 473c5f0..c4525ca 100644
--- a/src/reflock.h
+++ b/src/reflock.h
@@ -19,8 +19,6 @@
  * should use another lock to guarantee that this can't happen.
  */
 
-#include <stdint.h>
-
 #include "internal.h"
 
 typedef struct reflock {
diff --git a/src/sock.c b/src/sock.c
index 3fd0cad..bad7d5c 100644
--- a/src/sock.c
+++ b/src/sock.c
@@ -1,14 +1,17 @@
 #include <assert.h>
-#include <malloc.h>
 #include <stdbool.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include "afd.h"
 #include "error.h"
 #include "poll-group.h"
 #include "port.h"
+#include "queue.h"
 #include "sock.h"
+#include "tree.h"
+#include "util.h"
 #include "wepoll.h"
 #include "ws.h"
 
diff --git a/src/sock.h b/src/sock.h
index ea531ed..c316ccd 100644
--- a/src/sock.h
+++ b/src/sock.h
@@ -1,17 +1,14 @@
 #ifndef WEPOLL_SOCK_H_
 #define WEPOLL_SOCK_H_
 
-#include <stdint.h>
-
 #include "internal.h"
-#include "queue.h"
-#include "tree.h"
-#include "util.h"
 #include "wepoll.h"
 #include "win.h"
 
 typedef struct port_state port_state_t;
+typedef struct queue_node queue_node_t;
 typedef struct sock_state sock_state_t;
+typedef struct tree_node tree_node_t;
 
 WEPOLL_INTERNAL sock_state_t* sock_new(port_state_t* port_state,
                                        SOCKET socket);
diff --git a/src/tree.c b/src/tree.c
index 76dfa00..b6750a3 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -4,6 +4,7 @@
 #include <string.h>
 
 #include "tree.h"
+#include "util.h"
 
 void tree_init(tree_t* tree) {
   memset(tree, 0, sizeof *tree);
diff --git a/src/tree.h b/src/tree.h
index 139e13f..1e01257 100644
--- a/src/tree.h
+++ b/src/tree.h
@@ -5,7 +5,6 @@
 #include <stdint.h>
 
 #include "internal.h"
-#include "util.h"
 
 /* N.b.: the tree functions do not set errno or LastError when they fail. Each
  * of the API functions has at most one failure mode. It is up to the caller to
diff --git a/src/util.h b/src/util.h
index d767bdb..0bd90d5 100644
--- a/src/util.h
+++ b/src/util.h
@@ -1,12 +1,9 @@
 #ifndef WEPOLL_UTIL_H_
 #define WEPOLL_UTIL_H_
 
-#include <assert.h>
 #include <stddef.h>
 #include <stdint.h>
 
-#include "internal.h"
-
 #define array_count(a) (sizeof(a) / (sizeof((a)[0])))
 
 /* clang-format off */
diff --git a/src/ws.c b/src/ws.c
index 74b6bdf..83de065 100644
--- a/src/ws.c
+++ b/src/ws.c
@@ -1,8 +1,6 @@
-#include <malloc.h>
 #include <stdlib.h>
 
 #include "error.h"
-#include "util.h"
 #include "win.h"
 #include "ws.h"
 
diff --git a/src/ws.h b/src/ws.h
index d688d27..34ce5bb 100644
--- a/src/ws.h
+++ b/src/ws.h
@@ -2,7 +2,6 @@
 #define WEPOLL_WS_H_
 
 #include "internal.h"
-#include "util.h"
 #include "win.h"
 
 WEPOLL_INTERNAL int ws_global_init(void);
diff --git a/test/test-auto-drop-on-close.c b/test/test-auto-drop-on-close.c
index dd82778..2cdaf7e 100644
--- a/test/test-auto-drop-on-close.c
+++ b/test/test-auto-drop-on-close.c
@@ -10,6 +10,7 @@
  */
 
 #include <errno.h>
+#include <stdint.h>
 #include <stdlib.h>
 
 #include "test-util.h"
diff --git a/test/test-connect-fail-events.c b/test/test-connect-fail-events.c
index 1c28183..457d2e4 100644
--- a/test/test-connect-fail-events.c
+++ b/test/test-connect-fail-events.c
@@ -2,7 +2,6 @@
 #include <stdlib.h>
 
 #include "test-util.h"
-#include "util.h"
 #include "wepoll.h"
 #include "win.h"
 
diff --git a/test/test-connect-success-events.c b/test/test-connect-success-events.c
index 525fb71..ebc0fda 100644
--- a/test/test-connect-success-events.c
+++ b/test/test-connect-success-events.c
@@ -8,6 +8,7 @@
 
 #include <errno.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include "test-util.h"
 #include "util.h"
diff --git a/test/test-ctl-fuzz.c b/test/test-ctl-fuzz.c
index 72bf47e..85e57ab 100644
--- a/test/test-ctl-fuzz.c
+++ b/test/test-ctl-fuzz.c
@@ -1,4 +1,3 @@
-#include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
diff --git a/test/test-leak-1.c b/test/test-leak-1.c
index 6364dfc..efca1b5 100644
--- a/test/test-leak-1.c
+++ b/test/test-leak-1.c
@@ -1,10 +1,6 @@
-#include <errno.h>
-#include <stdbool.h>
-#include <stdio.h>
 #include <stdlib.h>
 
 #include "test-util.h"
-#include "util.h"
 #include "wepoll.h"
 #include "win.h"
 
diff --git a/test/test-mixed-socket-types.c b/test/test-mixed-socket-types.c
index bf36c51..90bb534 100644
--- a/test/test-mixed-socket-types.c
+++ b/test/test-mixed-socket-types.c
@@ -1,7 +1,5 @@
-#include <stdio.h>
 #include <stdlib.h>
 
-#include "error.h"
 #include "test-util.h"
 #include "wepoll.h"
 #include "win.h"
diff --git a/test/test-multi-poll.c b/test/test-multi-poll.c
index 894d3ca..80f869b 100644
--- a/test/test-multi-poll.c
+++ b/test/test-multi-poll.c
@@ -4,7 +4,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "init.h"
 #include "test-util.h"
 #include "util.h"
 #include "wepoll.h"
diff --git a/test/test-oneshot-and-hangup.c b/test/test-oneshot-and-hangup.c
index 7016fc9..7aaf207 100644
--- a/test/test-oneshot-and-hangup.c
+++ b/test/test-oneshot-and-hangup.c
@@ -1,6 +1,5 @@
 #include <errno.h>
 #include <stdbool.h>
-#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/test/test-reflock.c b/test/test-reflock.c
index e342518..727d80a 100644
--- a/test/test-reflock.c
+++ b/test/test-reflock.c
@@ -1,5 +1,6 @@
 #include <process.h>
 #include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 
diff --git a/test/test-tree.c b/test/test-tree.c
index de1842a..d6f1a0d 100644
--- a/test/test-tree.c
+++ b/test/test-tree.c
@@ -1,8 +1,5 @@
-#include <malloc.h>
-#include <stdbool.h>
 #include <stdint.h>
 #include <stdlib.h>
-#include <string.h>
 
 #include "test-util.h"
 #include "tree.h"
diff --git a/test/test-udp-pings.c b/test/test-udp-pings.c
index bc6dacc..0f92643 100644
--- a/test/test-udp-pings.c
+++ b/test/test-udp-pings.c
@@ -1,7 +1,7 @@
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 
-#include "error.h"
 #include "test-util.h"
 #include "wepoll.h"
 #include "win.h"