diff --git a/Makefile b/Makefile
index 217477c..9db32d4 100644
--- a/Makefile
+++ b/Makefile
@@ -67,15 +67,9 @@ $(TARGETS_TEST): test-%: %
 $(TARGETS_MEM_TEST): test-mem-%: %
 	valgrind --tool=memcheck --error-exitcode=1 --track-origins=yes --leak-check=full ./$^
 
-test-mem: build-test
-	@ $(foreach bin,$(BINS_TEST),valgrind --tool=memcheck --error-exitcode=1 \
-		--track-origins=yes --leak-check=full ./$(bin);)
-
 .PHONY: build-test
 build-test: $(BINS_TEST)
 
-# For simplicity, we link every object file to each of the test files. This
-# might be changed later if this starts to become too slow.
 $(BINS_TEST): %: %.c.o $(LIB)
 	$(CC) \
 		$^ -o $@
diff --git a/include/vieter_tree.h b/include/vieter_tree.h
index 2079eb9..4da500f 100644
--- a/include/vieter_tree.h
+++ b/include/vieter_tree.h
@@ -67,4 +67,22 @@ void vieter_tree_iterator_free(vieter_tree_iterator **ptp);
 vieter_tree_error vieter_tree_iterator_next(void **out,
                                             vieter_tree_iterator *iter);
 
+/*
+ * Acquire a read lock on the tree. Return value is the result of
+ * pthread_rwlock_rdlock.
+ */
+int vieter_tree_rlock(vieter_tree *tree);
+
+/*
+ * Acquire a write lock on the tree. Return value is the result of
+ * pthread_rwlock_wrlock.
+ */
+int vieter_tree_wlock(vieter_tree *tree);
+
+/*
+ * Unlock the lock after having acquired it. Return value is the result of
+ * pthread_rwlock_unlock.
+ */
+int vieter_tree_unlock(vieter_tree *tree);
+
 #endif
diff --git a/src/tree/vieter_tree.c b/src/tree/vieter_tree.c
index 84a1a26..ca6016e 100644
--- a/src/tree/vieter_tree.c
+++ b/src/tree/vieter_tree.c
@@ -114,3 +114,15 @@ bool vieter_tree_validate(vieter_tree *tree) {
   return vieter_tree_node_get(tree->root, vieter_tree_node_black) &&
          vieter_tree_node_validate(tree->root, 0, expected_black_nodes);
 }
+
+int vieter_tree_rlock(vieter_tree *tree) {
+  return pthread_rwlock_rdlock(&tree->lock);
+}
+
+int vieter_tree_wlock(vieter_tree *tree) {
+  return pthread_rwlock_wrlock(&tree->lock);
+}
+
+int vieter_tree_unlock(vieter_tree *tree) {
+  return pthread_rwlock_unlock(&tree->lock);
+}
diff --git a/src/tree/vieter_tree_internal.h b/src/tree/vieter_tree_internal.h
index 1214572..037345c 100644
--- a/src/tree/vieter_tree_internal.h
+++ b/src/tree/vieter_tree_internal.h
@@ -1,11 +1,13 @@
 #include "vieter_tree.h"
 #include "vieter_tree_node.h"
 
+#include <pthread.h>
 #include <stdbool.h>
 
 struct vieter_tree {
   uint64_t size;
   vieter_tree_node *root;
+  pthread_rwlock_t lock;
 };
 
 /*