diff --git a/c/2024/19/linen_layout.c b/c/2024/19/linen_layout.c
index 328cd35..8bcbe8f 100644
--- a/c/2024/19/linen_layout.c
+++ b/c/2024/19/linen_layout.c
@@ -25,20 +25,20 @@ bool towels_valid_design(Towels *t, char *design) {
 
 long towels_valid_designs(Towels *t, char *design) {
   AocHashmapNode *memo = aoc_hashmap_get(t->map, design);
-  if (memo != NULL) return memo->value;
+  if (memo != NULL) return *(long *)memo->value;
 
   if (strlen(design) == 0) return 1;
 
-  long valid_designs = 0;
+  long *valid_designs = malloc(sizeof(long));
   for (int i = 0; i < t->towels_count; i++) {
     if (strstr(design, t->towels[i]) == design) {
-      valid_designs += towels_valid_designs(t, design + strlen(t->towels[i]));
+      *valid_designs += towels_valid_designs(t, design + strlen(t->towels[i]));
     }
   }
 
   aoc_hashmap_put(t->map, design, valid_designs);
 
-  return valid_designs;
+  return *valid_designs;
 }
 
 int main() {
diff --git a/c/lib/hashmap.h b/c/lib/hashmap.h
index 1c81d16..0bdc575 100644
--- a/c/lib/hashmap.h
+++ b/c/lib/hashmap.h
@@ -16,7 +16,7 @@ typedef struct AocHashmapNode AocHashmapNode;
 
 typedef struct AocHashmapNode {
   char *key;
-  long value;
+  void *value;
   AocHashmapNode *next;
 } AocHashmapNode;
 
@@ -31,7 +31,7 @@ AocHashmapNode *aoc_hashmap_get(AocHashmap *map, char *key) {
   return node;
 }
 
-void *aoc_hashmap_put(AocHashmap *map, char *key, long value) {
+void *aoc_hashmap_put(AocHashmap *map, char *key, void *value) {
   int hash = aoc_hash(key);
   AocHashmapNode *node = map->buckets[hash];
   while (node != NULL) node = node->next;