diff --git a/src/runtime/stack.c b/src/runtime/stack.c
index 50f9f763..e272157c 100644
--- a/src/runtime/stack.c
+++ b/src/runtime/stack.c
@@ -8,6 +8,7 @@ static TSStateId INITIAL_STATE = 0;
 TSStack ts_stack_make() {
   TSStack result = {
     .entries = calloc(INITIAL_STACK_SIZE, sizeof(*result.entries)), .size = 0,
+    .capacity = INITIAL_STACK_SIZE,
   };
   return result;
 }
@@ -30,6 +31,10 @@ TSTree *ts_stack_top_node(const TSStack *stack) {
 }
 
 void ts_stack_push(TSStack *stack, TSStateId state, TSTree *node) {
+  if (stack->size == stack->capacity) {
+    stack->capacity *= 2;
+    stack->entries = realloc(stack->entries, stack->capacity * sizeof(*stack->entries));
+  }
   stack->entries[stack->size].state = state;
   stack->entries[stack->size].node = node;
   stack->size++;
diff --git a/src/runtime/stack.h b/src/runtime/stack.h
index ba523e56..2ba2582a 100644
--- a/src/runtime/stack.h
+++ b/src/runtime/stack.h
@@ -9,6 +9,7 @@ extern "C" {
 
 typedef struct {
   size_t size;
+  size_t capacity;
   struct {
     TSTree *node;
     TSStateId state;