diff --git a/source/s3.c b/source/s3.c
index 38020b087..e6390b485 100644
--- a/source/s3.c
+++ b/source/s3.c
@@ -121,13 +121,17 @@ AWS_STATIC_STRING_FROM_LITERAL(s_CopyObject_str, "CopyObject");
 AWS_STATIC_STRING_FROM_LITERAL(s_PutObject_str, "PutObject");
 AWS_STATIC_STRING_FROM_LITERAL(s_CreateSession_str, "CreateSession");
 
+static bool s_byte_cursor_eq_ignore_case(const void *a, const void *b) {
+    return aws_byte_cursor_eq_ignore_case(a, b);
+}
+
 static void s_s3_request_type_info_init(struct aws_allocator *allocator) {
     int err = aws_hash_table_init(
         &s_s3_operation_name_to_request_type_table,
         allocator,
         AWS_ARRAY_SIZE(s_s3_request_type_info_array) /*initial_size*/,
         aws_hash_byte_cursor_ptr_ignore_case,
-        (aws_hash_callback_eq_fn *)aws_byte_cursor_eq_ignore_case,
+        s_byte_cursor_eq_ignore_case,
         NULL /*destroy_key*/,
         NULL /*destroy_value*/);
     AWS_FATAL_ASSERT(!err);
diff --git a/source/s3_checksum_stream.c b/source/s3_checksum_stream.c
index 8f4f575c8..6d11df32d 100644
--- a/source/s3_checksum_stream.c
+++ b/source/s3_checksum_stream.c
@@ -105,6 +105,10 @@ static void s_aws_input_checksum_stream_destroy(struct aws_checksum_stream *impl
     aws_mem_release(impl->allocator, impl);
 }
 
+static void s_aws_input_checksum_stream_destroy_wrap(void *user_data) {
+    s_aws_input_checksum_stream_destroy(user_data);
+}
+
 static struct aws_input_stream_vtable s_aws_input_checksum_stream_vtable = {
     .seek = s_aws_input_checksum_stream_seek,
     .read = s_aws_input_checksum_stream_read,
@@ -129,7 +133,7 @@ static struct aws_checksum_stream *s_aws_checksum_input_checksum_stream_new(
     aws_byte_buf_init(&impl->checksum_result, allocator, impl->checksum->digest_size);
     impl->old_stream = aws_input_stream_acquire(existing_stream);
     aws_ref_count_init(
-        &impl->base.ref_count, impl, (aws_simple_completion_callback *)s_aws_input_checksum_stream_destroy);
+        &impl->base.ref_count, impl, s_aws_input_checksum_stream_destroy_wrap);
     return impl;
 on_error:
     aws_mem_release(impl->allocator, impl);
diff --git a/source/s3_chunk_stream.c b/source/s3_chunk_stream.c
index afea50b40..07bea1141 100644
--- a/source/s3_chunk_stream.c
+++ b/source/s3_chunk_stream.c
@@ -167,6 +167,10 @@ static void s_aws_input_chunk_stream_destroy(struct aws_chunk_stream *impl) {
     }
 }
 
+static void s_aws_input_chunk_stream_destroy_wrap(void *user_data) {
+    s_aws_input_chunk_stream_destroy(user_data);
+}
+
 static struct aws_input_stream_vtable s_aws_input_chunk_stream_vtable = {
     .seek = s_aws_input_chunk_stream_seek,
     .read = s_aws_input_chunk_stream_read,
@@ -257,7 +261,7 @@ struct aws_input_stream *aws_chunk_stream_new(
                    checksum_context->encoded_checksum_size + post_trailer_len;
 
     AWS_ASSERT(impl->current_stream);
-    aws_ref_count_init(&impl->base.ref_count, impl, (aws_simple_completion_callback *)s_aws_input_chunk_stream_destroy);
+    aws_ref_count_init(&impl->base.ref_count, impl, s_aws_input_chunk_stream_destroy_wrap);
     return &impl->base;
 
 error:
diff --git a/source/s3_default_buffer_pool.c b/source/s3_default_buffer_pool.c
index 074f09476..c7456cf2b 100644
--- a/source/s3_default_buffer_pool.c
+++ b/source/s3_default_buffer_pool.c
@@ -185,6 +185,10 @@ static void s_destroy_special_block_list(void *val) {
     aws_mem_release(special_list->allocator, special_list);
 }
 
+static void s_aws_s3_default_buffer_pool_destroy_wrap(void *user_data) {
+    aws_s3_default_buffer_pool_destroy(user_data);
+}
+
 struct aws_s3_buffer_pool *aws_s3_default_buffer_pool_new(
     struct aws_allocator *allocator,
     struct aws_s3_buffer_pool_config config) {
@@ -295,7 +299,7 @@ struct aws_s3_buffer_pool *aws_s3_default_buffer_pool_new(
     struct aws_s3_buffer_pool *pool = aws_mem_calloc(buffer_pool->base_allocator, 1, sizeof(struct aws_s3_buffer_pool));
     pool->impl = buffer_pool;
     pool->vtable = &s_default_pool_vtable;
-    aws_ref_count_init(&pool->ref_count, pool, (aws_simple_completion_callback *)aws_s3_default_buffer_pool_destroy);
+    aws_ref_count_init(&pool->ref_count, pool, s_aws_s3_default_buffer_pool_destroy_wrap);
 
     return pool;
 }
diff --git a/source/s3_parallel_input_stream.c b/source/s3_parallel_input_stream.c
index c7a730b52..211994ec4 100644
--- a/source/s3_parallel_input_stream.c
+++ b/source/s3_parallel_input_stream.c
@@ -17,6 +17,11 @@
 
 AWS_STATIC_STRING_FROM_LITERAL(s_readonly_bytes_mode, "rb");
 
+static void s_parallel_stream_vtable_destroy_wrap(void *user_data) {
+    struct aws_parallel_input_stream *stream = user_data;
+    stream->vtable->destroy(stream);
+}
+
 void aws_parallel_input_stream_init_base(
     struct aws_parallel_input_stream *stream,
     struct aws_allocator *alloc,
@@ -28,7 +33,7 @@ void aws_parallel_input_stream_init_base(
     stream->vtable = vtable;
     stream->impl = impl;
     stream->shutdown_future = aws_future_void_new(alloc);
-    aws_ref_count_init(&stream->ref_count, stream, (aws_simple_completion_callback *)vtable->destroy);
+    aws_ref_count_init(&stream->ref_count, stream, s_parallel_stream_vtable_destroy_wrap);
 }
 
 struct aws_parallel_input_stream *aws_parallel_input_stream_acquire(struct aws_parallel_input_stream *stream) {
diff --git a/source/s3_platform_info.c b/source/s3_platform_info.c
index fd0694ec4..0b4d49f86 100644
--- a/source/s3_platform_info.c
+++ b/source/s3_platform_info.c
@@ -152,6 +152,10 @@ static void s_destroy_loader(void *arg) {
     aws_mem_release(loader->allocator, loader);
 }
 
+static bool s_byte_cursor_eq_ignore_case(const void *a, const void *b) {
+    return aws_byte_cursor_eq_ignore_case(a, b);
+}
+
 struct aws_s3_platform_info_loader *aws_s3_platform_info_loader_new(struct aws_allocator *allocator) {
     struct aws_s3_platform_info_loader *loader =
         aws_mem_calloc(allocator, 1, sizeof(struct aws_s3_platform_info_loader));
@@ -175,7 +179,7 @@ struct aws_s3_platform_info_loader *aws_s3_platform_info_loader_new(struct aws_a
             allocator,
             32,
             aws_hash_byte_cursor_ptr_ignore_case,
-            (aws_hash_callback_eq_fn *)aws_byte_cursor_eq_ignore_case,
+            s_byte_cursor_eq_ignore_case,
             NULL,
             NULL) &&
         "Hash table init failed!");
diff --git a/source/s3express_credentials_provider.c b/source/s3express_credentials_provider.c
index 7afb5aca3..ee1001fb4 100644
--- a/source/s3express_credentials_provider.c
+++ b/source/s3express_credentials_provider.c
@@ -914,6 +914,11 @@ static void s_bg_refresh_task(struct aws_task *task, void *arg, enum aws_task_st
     }
 }
 
+static void s_provider_vtable_destroy_wrap(void *user_data) {
+    struct aws_s3express_credentials_provider *provider = user_data;
+    provider->vtable->destroy(provider);
+}
+
 void aws_s3express_credentials_provider_init_base(
     struct aws_s3express_credentials_provider *provider,
     struct aws_allocator *allocator,
@@ -926,7 +931,19 @@ void aws_s3express_credentials_provider_init_base(
     provider->allocator = allocator;
     provider->vtable = vtable;
     provider->impl = impl;
-    aws_ref_count_init(&provider->ref_count, provider, (aws_simple_completion_callback *)provider->vtable->destroy);
+    aws_ref_count_init(&provider->ref_count, provider, s_provider_vtable_destroy_wrap);
+}
+
+static bool s_string_eq(const void *a, const void *b) {
+    return aws_string_eq(a, b);
+}
+
+static void s_s3express_session_destroy(void *value) {
+    s_aws_s3express_session_destroy(value);
+}
+
+static void s_finish_provider_destroy_wrap(void *user_data) {
+    s_finish_provider_destroy(user_data);
 }
 
 struct aws_s3express_credentials_provider *aws_s3express_credentials_provider_new_default(
@@ -969,9 +986,9 @@ struct aws_s3express_credentials_provider *aws_s3express_credentials_provider_ne
     impl->synced_data.cache = aws_cache_new_lru(
         allocator,
         aws_hash_string,
-        (aws_hash_callback_eq_fn *)aws_string_eq,
+        s_string_eq,
         NULL,
-        (aws_hash_callback_destroy_fn *)s_aws_s3express_session_destroy,
+        s_s3express_session_destroy,
         s_default_cache_capacity);
     AWS_ASSERT(impl->synced_data.cache);
 
@@ -989,7 +1006,7 @@ struct aws_s3express_credentials_provider *aws_s3express_credentials_provider_ne
     provider->shutdown_complete_callback = options->shutdown_complete_callback;
     provider->shutdown_user_data = options->shutdown_user_data;
     aws_mutex_init(&impl->synced_data.lock);
-    aws_ref_count_init(&impl->internal_ref, provider, (aws_simple_completion_callback *)s_finish_provider_destroy);
+    aws_ref_count_init(&impl->internal_ref, provider, s_finish_provider_destroy_wrap);
 
     /* Init the background refresh task */
     impl->bg_refresh_task = aws_mem_calloc(provider->allocator, 1, sizeof(struct aws_task));
diff --git a/tests/s3_data_plane_tests.c b/tests/s3_data_plane_tests.c
index 8323647aa..ba3a2c813 100644
--- a/tests/s3_data_plane_tests.c
+++ b/tests/s3_data_plane_tests.c
@@ -3448,6 +3448,10 @@ void s_failing_pool_destroy(struct aws_s3_buffer_pool *buffer_pool_wrapper) {
     aws_mem_release((struct aws_allocator *)buffer_pool_wrapper->impl, buffer_pool_wrapper);
 }
 
+static void s_failing_pool_destroy_wrap(void *user_data) {
+    s_failing_pool_destroy(user_data);
+}
+
 struct aws_s3_buffer_pool *s_always_error_buffer_pool_fn(
     struct aws_allocator *allocator,
     struct aws_s3_buffer_pool_config config,
@@ -3457,7 +3461,7 @@ struct aws_s3_buffer_pool *s_always_error_buffer_pool_fn(
     struct aws_s3_buffer_pool *pool = aws_mem_calloc(allocator, 1, sizeof(struct aws_s3_buffer_pool));
     pool->impl = allocator;
     pool->vtable = &s_failing_pool_vtable;
-    aws_ref_count_init(&pool->ref_count, pool, (aws_simple_completion_callback *)s_failing_pool_destroy);
+    aws_ref_count_init(&pool->ref_count, pool, s_failing_pool_destroy_wrap);
 
     return pool;
 }
diff --git a/tests/s3_s3express_client_test.c b/tests/s3_s3express_client_test.c
index eb3b6cb05..a6ccb2460 100644
--- a/tests/s3_s3express_client_test.c
+++ b/tests/s3_s3express_client_test.c
@@ -35,6 +35,10 @@ struct aws_s3express_client_tester {
 
 static struct aws_s3express_client_tester s_tester;
 
+static void s_credentials_release_wrap(void *value) {
+    aws_credentials_release(value);
+}
+
 static int s_s3express_client_tester_init(struct aws_allocator *allocator) {
     s_tester.allocator = allocator;
     aws_hash_table_init(
@@ -44,7 +48,7 @@ static int s_s3express_client_tester_init(struct aws_allocator *allocator) {
         aws_hash_string,
         aws_hash_callback_string_eq,
         aws_hash_callback_string_destroy,
-        (aws_hash_callback_destroy_fn *)aws_credentials_release);
+        s_credentials_release_wrap);
     aws_atomic_init_int(&s_tester.provider_requests_made, 0);
     return AWS_OP_SUCCESS;
 }
diff --git a/tests/s3_test_input_stream.c b/tests/s3_test_input_stream.c
index 1d4e5e020..7566bc0bc 100644
--- a/tests/s3_test_input_stream.c
+++ b/tests/s3_test_input_stream.c
@@ -93,6 +93,10 @@ static void s_aws_s3_test_input_stream_destroy(struct aws_s3_test_input_stream_i
     aws_mem_release(test_input_stream->allocator, test_input_stream);
 }
 
+static void s_aws_s3_test_input_stream_destroy_wrap(void *user_data) {
+    s_aws_s3_test_input_stream_destroy(user_data);
+}
+
 static struct aws_input_stream_vtable s_aws_s3_test_input_stream_vtable_1 = {
     .seek = s_aws_s3_test_input_stream_seek,
     .read = s_aws_s3_test_input_stream_read_1,
@@ -121,7 +125,7 @@ struct aws_input_stream *aws_s3_test_input_stream_new_with_value_type(
     aws_ref_count_init(
         &test_input_stream->base.ref_count,
         test_input_stream,
-        (aws_simple_completion_callback *)s_aws_s3_test_input_stream_destroy);
+        s_aws_s3_test_input_stream_destroy_wrap);
 
     struct aws_input_stream *input_stream = &test_input_stream->base;