diff --git a/src/port.c b/src/port.c
index 18fe6a1..62b76d8 100644
--- a/src/port.c
+++ b/src/port.c
@@ -347,11 +347,9 @@ int ep_port_register_socket_handle(ep_port_t* port_info,
   return 0;
 }
 
-int ep_port_unregister_socket_handle(ep_port_t* port_info,
-                                     ep_sock_t* sock_info) {
-  if (tree_del(&port_info->sock_tree, &sock_info->tree_node) < 0)
-    return_error(-1, ERROR_NOT_FOUND);
-  return 0;
+void ep_port_unregister_socket_handle(ep_port_t* port_info,
+                                      ep_sock_t* sock_info) {
+  tree_del(&port_info->sock_tree, &sock_info->tree_node);
 }
 
 ep_sock_t* ep_port_find_socket(ep_port_t* port_info, SOCKET socket) {
diff --git a/src/port.h b/src/port.h
index eefd423..326c93f 100644
--- a/src/port.h
+++ b/src/port.h
@@ -51,8 +51,8 @@ WEPOLL_INTERNAL void ep_port_release_poll_group(ep_port_t* port_info,
 WEPOLL_INTERNAL int ep_port_register_socket_handle(ep_port_t* port_info,
                                                    ep_sock_t* sock_info,
                                                    SOCKET socket);
-WEPOLL_INTERNAL int ep_port_unregister_socket_handle(ep_port_t* port_info,
-                                                     ep_sock_t* sock_info);
+WEPOLL_INTERNAL void ep_port_unregister_socket_handle(ep_port_t* port_info,
+                                                      ep_sock_t* sock_info);
 WEPOLL_INTERNAL ep_sock_t* ep_port_find_socket(ep_port_t* port_info,
                                                SOCKET socket);
 
diff --git a/src/tree.c b/src/tree.c
index d742b95..7d304ec 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -1,23 +1,56 @@
-#include <assert.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
 
-#include "error.h"
-#include "rb.h"
 #include "tree.h"
-#include "util.h"
 
-static inline int _tree_compare(tree_node_t* a, tree_node_t* b) {
-  if (a->key < b->key)
-    return -1;
-  else if (a->key > b->key)
-    return 1;
-  else
-    return 0;
+static void _tree_rotate_left(tree_t* tree, tree_node_t* node) {
+  tree_node_t* p = node;
+  tree_node_t* q = node->right;
+  tree_node_t* parent = p->parent;
+
+  if (parent) {
+    if (parent->left == p)
+      parent->left = q;
+    else
+      parent->right = q;
+  } else {
+    tree->root = q;
+  }
+
+  q->parent = parent;
+  p->parent = q;
+  p->right = q->left;
+  if (p->right)
+    p->right->parent = p;
+  q->left = p;
 }
 
-RB_GENERATE_STATIC(tree, tree_node, node, _tree_compare);
+static void _tree_rotate_right(tree_t* tree, tree_node_t* node) {
+  tree_node_t* p = node;
+  tree_node_t* q = node->left;
+  tree_node_t* parent = p->parent;
+
+  if (parent) {
+    if (parent->left == p)
+      parent->left = q;
+    else
+      parent->right = q;
+  } else {
+    tree->root = q;
+  }
+
+  q->parent = parent;
+  p->parent = q;
+  p->left = q->right;
+  if (p->left)
+    p->left->parent = p;
+  q->right = p;
+}
 
 void tree_init(tree_t* tree) {
-  RB_INIT(tree);
+  memset(tree, 0, sizeof *tree);
 }
 
 void tree_node_init(tree_node_t* node) {
@@ -25,39 +58,210 @@ void tree_node_init(tree_node_t* node) {
 }
 
 int tree_add(tree_t* tree, tree_node_t* node, uintptr_t key) {
-  tree_node_t* existing_node;
+  tree_node_t* parent;
+  tree_node_t* grandparent;
+  tree_node_t* uncle;
+
+  parent = tree->root;
+  if (parent) {
+    for (;;) {
+      if (key < parent->key) {
+        if (parent->left) {
+          parent = parent->left;
+        } else {
+          parent->left = node;
+          break;
+        }
+      } else if (key > parent->key) {
+        if (parent->right) {
+          parent = parent->right;
+        } else {
+          parent->right = node;
+          break;
+        }
+      } else {
+        return -1;
+      }
+    }
+  } else {
+    tree->root = node;
+  }
 
   node->key = key;
-  existing_node = RB_INSERT(tree, tree, node);
+  node->left = node->right = NULL;
+  node->parent = parent;
+  node->red = true;
 
-  if (existing_node != NULL)
-    return -1;
+  while (parent && parent->red) {
+    grandparent = parent->parent;
+    if (parent == grandparent->left) {
+      uncle = grandparent->right;
+      if (uncle && uncle->red) {
+        parent->red = uncle->red = false;
+        grandparent->red = true;
+        node = grandparent;
+      } else {
+        if (node == parent->right) {
+          _tree_rotate_left(tree, parent);
+          node = parent;
+          parent = node->parent;
+        }
+        parent->red = false;
+        grandparent->red = true;
+        _tree_rotate_right(tree, grandparent);
+      }
+    } else {
+      uncle = grandparent->left;
+      if (uncle && uncle->red) {
+        parent->red = uncle->red = false;
+        grandparent->red = true;
+        node = grandparent;
+      } else {
+        if (node == parent->left) {
+          _tree_rotate_right(tree, parent);
+          node = parent;
+          parent = node->parent;
+        }
+        parent->red = false;
+        grandparent->red = true;
+        _tree_rotate_left(tree, grandparent);
+      }
+    }
+    parent = node->parent;
+  }
+  tree->root->red = false;
 
   return 0;
 }
 
-int tree_del(tree_t* tree, tree_node_t* node) {
-  tree_node_t* removed_node;
+void tree_del(tree_t* tree, tree_node_t* node) {
+  tree_node_t* parent = node->parent;
+  tree_node_t* left = node->left;
+  tree_node_t* right = node->right;
+  tree_node_t* next;
+  tree_node_t* sibling;
+  bool red;
 
-  removed_node = RB_REMOVE(tree, tree, node);
+  if (!left) {
+    next = right;
+  } else if (!right) {
+    next = left;
+  } else {
+    next = right;
+    while (next->left)
+      next = next->left;
+  }
 
-  if (removed_node == NULL)
-    return -1;
-  else
-    assert(removed_node == node);
+  if (parent) {
+    if (parent->left == node)
+      parent->left = next;
+    else
+      parent->right = next;
+  } else {
+    tree->root = next;
+  }
 
-  return 0;
+  if (left && right) {
+    red = next->red;
+    next->red = node->red;
+    next->left = left;
+    left->parent = next;
+    if (next != right) {
+      parent = next->parent;
+      next->parent = node->parent;
+      node = next->right;
+      parent->left = node;
+      next->right = right;
+      right->parent = next;
+    } else {
+      next->parent = parent;
+      parent = next;
+      node = next->right;
+    }
+  } else {
+    red = node->red;
+    node = next;
+  }
+
+  if (node)
+    node->parent = parent;
+  if (red)
+    return;
+  if (node && node->red) {
+    node->red = false;
+    return;
+  }
+
+  do {
+    if (node == tree->root)
+      break;
+    if (node == parent->left) {
+      sibling = parent->right;
+      if (sibling->red) {
+        sibling->red = false;
+        parent->red = true;
+        _tree_rotate_left(tree, parent);
+        sibling = parent->right;
+      }
+      if ((sibling->left && sibling->left->red) ||
+          (sibling->right && sibling->right->red)) {
+        if (!sibling->right || !sibling->right->red) {
+          sibling->left->red = false;
+          sibling->red = true;
+          _tree_rotate_right(tree, sibling);
+          sibling = parent->right;
+        }
+        sibling->red = parent->red;
+        parent->red = sibling->right->red = false;
+        _tree_rotate_left(tree, parent);
+        node = tree->root;
+        break;
+      }
+    } else {
+      sibling = parent->left;
+      if (sibling->red) {
+        sibling->red = false;
+        parent->red = true;
+        _tree_rotate_right(tree, parent);
+        sibling = parent->left;
+      }
+      if ((sibling->left && sibling->left->red) ||
+          (sibling->right && sibling->right->red)) {
+        if (!sibling->left || !sibling->left->red) {
+          sibling->right->red = false;
+          sibling->red = true;
+          _tree_rotate_left(tree, sibling);
+          sibling = parent->left;
+        }
+        sibling->red = parent->red;
+        parent->red = sibling->left->red = false;
+        _tree_rotate_right(tree, parent);
+        node = tree->root;
+        break;
+      }
+    }
+    sibling->red = true;
+    node = parent;
+    parent = parent->parent;
+  } while (!node->red);
+
+  if (node)
+    node->red = false;
 }
 
-tree_node_t* tree_find(tree_t* tree, uintptr_t key) {
-  tree_node_t lookup;
-
-  memset(&lookup, 0, sizeof lookup);
-  lookup.key = key;
-
-  return RB_FIND(tree, tree, &lookup);
+tree_node_t* tree_find(const tree_t* tree, uintptr_t key) {
+  tree_node_t* node = tree->root;
+  while (node) {
+    if (key < node->key)
+      node = node->left;
+    else if (key > node->key)
+      node = node->right;
+    else
+      return node;
+  }
+  return NULL;
 }
 
-tree_node_t* tree_root(tree_t* tree) {
-  return RB_ROOT(tree);
+tree_node_t* tree_root(const tree_t* tree) {
+  return tree->root;
 }
diff --git a/src/tree.h b/src/tree.h
index b9857dc..d1c58ea 100644
--- a/src/tree.h
+++ b/src/tree.h
@@ -1,28 +1,39 @@
 #ifndef WEPOLL_TREE_H_
 #define WEPOLL_TREE_H_
 
+#include <stdbool.h>
+#include <stdint.h>
+
 #include "internal.h"
-#include "rb.h"
+#include "util.h"
 
 /* NB: 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
  * set an appropriate error code when necessary.
  */
 
-typedef RB_HEAD(tree, tree_node) tree_t;
+typedef struct tree tree_t;
+typedef struct tree_node tree_node_t;
+
+typedef struct tree {
+  tree_node_t* root;
+} tree_t;
 
 typedef struct tree_node {
-  RB_ENTRY(tree_node) node;
+  tree_node_t* left;
+  tree_node_t* right;
+  tree_node_t* parent;
   uintptr_t key;
+  bool red;
 } tree_node_t;
 
 WEPOLL_INTERNAL void tree_init(tree_t* tree);
 WEPOLL_INTERNAL void tree_node_init(tree_node_t* node);
 
 WEPOLL_INTERNAL int tree_add(tree_t* tree, tree_node_t* node, uintptr_t key);
-WEPOLL_INTERNAL int tree_del(tree_t* tree, tree_node_t* node);
+WEPOLL_INTERNAL void tree_del(tree_t* tree, tree_node_t* node);
 
-WEPOLL_INTERNAL tree_node_t* tree_find(tree_t* tree, uintptr_t key);
-WEPOLL_INTERNAL tree_node_t* tree_root(tree_t* tree);
+WEPOLL_INTERNAL tree_node_t* tree_find(const tree_t* tree, uintptr_t key);
+WEPOLL_INTERNAL tree_node_t* tree_root(const tree_t* tree);
 
 #endif /* WEPOLL_TREE_H_ */
diff --git a/test/test-tree.c b/test/test-tree.c
new file mode 100644
index 0000000..dd26596
--- /dev/null
+++ b/test/test-tree.c
@@ -0,0 +1,179 @@
+#include <malloc.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "test-util.h"
+#include "tree.h"
+#include "util.h"
+
+#define NODE_COUNT 1000
+static_assert(NODE_COUNT <= RAND_MAX, "NODE_COUNT too high");
+
+typedef void (*test_op_t)(tree_t* tree, uintptr_t key);
+
+static size_t count_subtree(const tree_node_t* node) {
+  if (node == NULL)
+    return 0;
+  else
+    return 1 + count_subtree(node->left) + count_subtree(node->right);
+}
+
+static size_t count_tree(const tree_t* tree) {
+  return count_subtree(tree_root(tree));
+}
+
+static size_t check_subtree_structure(const tree_node_t* node) {
+  size_t black_height_left;
+  size_t black_height_right;
+
+  if (!node)
+    return 0;
+
+  black_height_left = check_subtree_structure(node->left);
+  black_height_right = check_subtree_structure(node->right);
+  check(black_height_left == black_height_right);
+
+  if (node->red) {
+    check(!node->left || !node->left->red);
+    check(!node->right || !node->right->red);
+    return black_height_left;
+  } else {
+    return black_height_left + 1;
+  }
+}
+
+static void check_tree_structure(const tree_t* tree) {
+  check_subtree_structure(tree_root(tree));
+}
+
+static void check_tree_count(const tree_t* tree, size_t expected_count) {
+  size_t count = count_tree(tree);
+  check(count == expected_count);
+}
+
+static void keys_increasing(tree_t* tree, test_op_t op) {
+  ssize_t i;
+  for (i = 0; i < NODE_COUNT; i++)
+    op(tree, i);
+}
+
+static void keys_decreasing(tree_t* tree, test_op_t op) {
+  ssize_t i;
+  for (i = NODE_COUNT - 1; i >= 0; i--)
+    op(tree, i);
+}
+
+static void keys_random(tree_t* tree, test_op_t op) {
+  uintptr_t keys[NODE_COUNT];
+  uintptr_t index, key;
+  ssize_t left;
+
+  for (index = 0; index < NODE_COUNT; index++)
+    keys[index] = index;
+
+  for (left = NODE_COUNT - 1; left >= 0; left--) {
+    index = left > 0 ? rand() % left : 0;
+    key = keys[index];
+    keys[index] = keys[left];
+    op(tree, key);
+  };
+}
+
+static void add(tree_t* tree, uintptr_t key) {
+  tree_node_t* node;
+  size_t before_count;
+  int r;
+
+  before_count = count_tree(tree);
+
+  node = malloc(sizeof *node);
+  check(node != NULL);
+  tree_node_init(node);
+
+  r = tree_add(tree, node, key);
+  check(r == 0);
+  check(node->key == key);
+
+  check_tree_structure(tree);
+  check_tree_count(tree, before_count + 1);
+}
+
+static void add_error(tree_t* tree, uintptr_t key) {
+  tree_node_t node;
+  size_t before_count;
+  int r;
+
+  before_count = count_tree(tree);
+
+  tree_node_init(&node);
+  r = tree_add(tree, &node, key);
+  check(r == -1);
+
+  check_tree_structure(tree);
+  check_tree_count(tree, before_count);
+}
+
+static void find_del(tree_t* tree, uintptr_t key) {
+  tree_node_t* node;
+  size_t before_count;
+
+  before_count = count_tree(tree);
+
+  node = tree_find(tree, key);
+  check(node != NULL);
+  check(node->key == key);
+
+  tree_del(tree, node);
+  free(node);
+
+  check_tree_structure(tree);
+  check_tree_count(tree, before_count - 1);
+}
+
+static void find_error(tree_t* tree, uintptr_t key) {
+  tree_node_t* node;
+  size_t before_count;
+
+  before_count = count_tree(tree);
+
+  node = tree_find(tree, key);
+  check(node == NULL);
+
+  check_tree_structure(tree);
+  check_tree_count(tree, before_count);
+}
+
+int main(void) {
+  tree_t tree;
+  tree_init(&tree);
+
+  keys_increasing(&tree, add);
+  check_tree_count(&tree, NODE_COUNT);
+  keys_increasing(&tree, add_error);
+  keys_increasing(&tree, find_del);
+  check_tree_count(&tree, 0);
+  keys_increasing(&tree, find_error);
+
+  keys_decreasing(&tree, add);
+  check_tree_count(&tree, NODE_COUNT);
+  keys_decreasing(&tree, add_error);
+  keys_decreasing(&tree, find_del);
+  check_tree_count(&tree, 0);
+  keys_decreasing(&tree, find_error);
+
+  keys_random(&tree, add);
+  check_tree_count(&tree, NODE_COUNT);
+  keys_random(&tree, add_error);
+  keys_random(&tree, find_del);
+  check_tree_count(&tree, 0);
+  keys_random(&tree, find_error);
+
+  keys_random(&tree, add);
+  check_tree_count(&tree, NODE_COUNT);
+  keys_increasing(&tree, add_error);
+  keys_decreasing(&tree, find_del);
+  check_tree_count(&tree, 0);
+  keys_random(&tree, find_error);
+}