diff --git a/ccc/private/private_buffer.h b/ccc/private/private_buffer.h
index 9a3c429f..2fcd8fa8 100644
--- a/ccc/private/private_buffer.h
+++ b/ccc/private/private_buffer.h
@@ -46,14 +46,6 @@ struct CCC_Buffer
     void *context;
 };
 
-/** @internal */
-#define CCC_private_buf_non_CCC_private_buf_default_size(...) __VA_ARGS__
-/** @internal */
-#define CCC_private_buf_default_size(...) 0
-/** @internal */
-#define CCC_private_buf_optional_size(...)                                     \
-    __VA_OPT__(CCC_private_buf_non_)##CCC_private_buf_default_size(__VA_ARGS__)
-
 /** @internal Initializes the Buffer with a default size of 0. However the user
 can specify that the Buffer has some count of elements from index
 `[0, capacity - 1)` at initialization time. The Buffer assumes these elements
@@ -175,4 +167,4 @@ of memory in one step. */
 
 /* NOLINTEND(readability-identifier-naming) */
 
-#endif /* CCC_PRIVATE_BUF_H */
+#endif /* CCC_PRIVATE_BUFFER_H */
diff --git a/source/bitset.c b/source/bitset.c
index 531263a3..75cf3fa8 100644
--- a/source/bitset.c
+++ b/source/bitset.c
@@ -1029,7 +1029,7 @@ CCC_Result
 CCC_bitset_reserve(CCC_Bitset *const bitset, size_t const to_add,
                    CCC_Allocator *const allocate)
 {
-    if (!bitset || !allocate)
+    if (!bitset || !allocate || !to_add)
     {
         return CCC_RESULT_ARGUMENT_ERROR;
     }
diff --git a/source/buffer.c b/source/buffer.c
index 8eb91250..0816788c 100644
--- a/source/buffer.c
+++ b/source/buffer.c
@@ -60,7 +60,7 @@ CCC_Result
 CCC_buffer_reserve(CCC_Buffer *const buffer, size_t const to_add,
                    CCC_Allocator *const allocate)
 {
-    if (!buffer || !allocate)
+    if (!buffer || !allocate || !to_add)
     {
         return CCC_RESULT_ARGUMENT_ERROR;
     }
diff --git a/source/flat_double_ended_queue.c b/source/flat_double_ended_queue.c
index 6e52c0c3..610047c3 100644
--- a/source/flat_double_ended_queue.c
+++ b/source/flat_double_ended_queue.c
@@ -360,7 +360,7 @@ CCC_flat_double_ended_queue_reserve(CCC_Flat_double_ended_queue *const queue,
                                     size_t const to_add,
                                     CCC_Allocator *const allocate)
 {
-    if (!queue || !allocate)
+    if (!queue || !allocate || !to_add)
     {
         return CCC_RESULT_ARGUMENT_ERROR;
     }
diff --git a/source/flat_hash_map.c b/source/flat_hash_map.c
index d1397ecf..c8e124cd 100644
--- a/source/flat_hash_map.c
+++ b/source/flat_hash_map.c
@@ -877,7 +877,7 @@ CCC_Result
 CCC_flat_hash_map_reserve(CCC_Flat_hash_map *const map, size_t const to_add,
                           CCC_Allocator *const allocate)
 {
-    if (unlikely(!map || !to_add || !allocate))
+    if (unlikely(!map || !to_add || !allocate || !to_add))
     {
         return CCC_RESULT_ARGUMENT_ERROR;
     }