diff --git a/spec/integration/corpus_specs.cc b/spec/integration/corpus_specs.cc
index a986a2d3..9d9cd191 100644
--- a/spec/integration/corpus_specs.cc
+++ b/spec/integration/corpus_specs.cc
@@ -1,16 +1,18 @@
 #include "spec_helper.h"
+#include "runtime/alloc.h"
 #include "helpers/test_languages.h"
 #include "helpers/read_test_entries.h"
 #include "helpers/spy_input.h"
 #include "helpers/log_debugger.h"
 #include "helpers/point_helpers.h"
 #include "helpers/encoding_helpers.h"
+#include "helpers/record_alloc.h"
 #include <set>
 
 static void expect_the_correct_tree(TSNode node, TSDocument *document, string tree_string) {
   const char *node_string = ts_node_string(node, document);
   AssertThat(node_string, Equals(tree_string));
-  free((void *)node_string);
+  ts_free((void *)node_string);
 }
 
 static void expect_a_consistent_tree(TSNode node, TSDocument *document) {
@@ -105,6 +107,7 @@ describe("The Corpus", []() {
       TSDocument *document;
 
       before_each([&]() {
+        record_alloc::start();
         document = ts_document_make();
         ts_document_set_language(document, get_test_language(language_name));
         // ts_document_set_debugger(document, log_debugger_make(true));
@@ -112,6 +115,7 @@ describe("The Corpus", []() {
 
       after_each([&]() {
         ts_document_free(document);
+        AssertThat(record_alloc::outstanding_allocation_indices(), IsEmpty());
       });
 
       for (auto &entry : read_corpus_entries(language_dir + "/grammar_test")) {
diff --git a/src/runtime/parser.c b/src/runtime/parser.c
index 10124325..76507e78 100644
--- a/src/runtime/parser.c
+++ b/src/runtime/parser.c
@@ -605,28 +605,35 @@ static ParseActionResult ts_parser__accept(TSParser *self, int head) {
         TSTree *root = pop_result->trees[i];
         size_t leading_extra_count = i;
         size_t trailing_extra_count = pop_result->tree_count - 1 - i;
-        TSTree **new_children = ts_calloc(
-          root->child_count + leading_extra_count + trailing_extra_count,
-          sizeof(TSTree *));
-        if (!new_children)
-          goto error;
-
-        if (leading_extra_count > 0)
-          memcpy(new_children, pop_result->trees,
-                 leading_extra_count * sizeof(TSTree *));
-        if (root->child_count > 0)
-          memcpy(new_children + leading_extra_count, root->children,
-                 root->child_count * sizeof(TSTree *));
-        if (trailing_extra_count > 0)
-          memcpy(new_children + leading_extra_count + root->child_count,
-                 pop_result->trees + leading_extra_count + 1,
-                 trailing_extra_count * sizeof(TSTree *));
         size_t new_count =
           root->child_count + leading_extra_count + trailing_extra_count;
-        ts_tree_set_children(root, new_count, new_children);
+
+        if (new_count > 0) {
+          TSTree **new_children = ts_calloc(new_count, sizeof(TSTree *));
+          if (!new_children)
+            goto error;
+          if (leading_extra_count > 0)
+            memcpy(new_children, pop_result->trees,
+                   leading_extra_count * sizeof(TSTree *));
+          if (root->child_count > 0)
+            memcpy(new_children + leading_extra_count, root->children,
+                   root->child_count * sizeof(TSTree *));
+          if (trailing_extra_count > 0)
+            memcpy(new_children + leading_extra_count + root->child_count,
+                   pop_result->trees + leading_extra_count + 1,
+                   trailing_extra_count * sizeof(TSTree *));
+          ts_tree_set_children(root, new_count, new_children);
+        }
+
         ts_parser__remove_head(self, pop_result->head_index);
-        self->finished_tree =
-          ts_parser__select_tree(self, self->finished_tree, root);
+        TSTree *tree = ts_parser__select_tree(self, self->finished_tree, root);
+        if (tree == root) {
+          ts_tree_release(self->finished_tree);
+          self->finished_tree = root;
+        } else {
+          ts_tree_release(root);
+        }
+
         ts_free(pop_result->trees);
         break;
       }
@@ -834,10 +841,8 @@ TSTree *ts_parser_parse(TSParser *self, TSInput input, TSTree *previous_tree) {
             ts_stack_head_count(self->stack),
             ts_stack_top_state(self->stack, head), position.chars);
 
-        if (position.chars == last_position.chars &&
-            ts_parser__can_reuse(self, head, lookahead)) {
-          ts_tree_retain(lookahead);
-        } else {
+        if (position.chars != last_position.chars ||
+            !ts_parser__can_reuse(self, head, lookahead)) {
           ts_tree_release(lookahead);
           lookahead = ts_parser__get_next_lookahead(self, head);
           if (!lookahead)
diff --git a/src/runtime/vector.h b/src/runtime/vector.h
index 6bc2ed20..4c33c9d8 100644
--- a/src/runtime/vector.h
+++ b/src/runtime/vector.h
@@ -28,6 +28,9 @@ static inline Vector vector_new(size_t element_size) {
 }
 
 static inline bool vector_grow(Vector *self, size_t capacity) {
+  if (capacity == 0)
+    return true;
+
   void *new_contents;
   if (self->contents)
     new_contents = ts_realloc(self->contents, capacity * self->element_size);