diff --git a/c/blake3_c_rust_bindings/src/lib.rs b/c/blake3_c_rust_bindings/src/lib.rs
index ac7880a5..31b7731b 100644
--- a/c/blake3_c_rust_bindings/src/lib.rs
+++ b/c/blake3_c_rust_bindings/src/lib.rs
@@ -291,6 +291,7 @@ pub mod ffi {
                 flags_end: u8,
                 out: *mut u8,
             );
+            #[cfg(unix)]
             pub fn blake3_xof_many_avx512(
                 cv: *const u32,
                 block: *const u8,
diff --git a/c/blake3_c_rust_bindings/src/test.rs b/c/blake3_c_rust_bindings/src/test.rs
index ec11219a..da883677 100644
--- a/c/blake3_c_rust_bindings/src/test.rs
+++ b/c/blake3_c_rust_bindings/src/test.rs
@@ -425,6 +425,7 @@ fn test_xof_many_portable() {
 }
 
 #[test]
+#[cfg(unix)]
 #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 fn test_xof_many_avx512() {
     if !crate::avx512_detected() {
diff --git a/c/blake3_dispatch.c b/c/blake3_dispatch.c
index 725f7ee1..a90c757c 100644
--- a/c/blake3_dispatch.c
+++ b/c/blake3_dispatch.c
@@ -230,7 +230,7 @@ void blake3_xof_many(const uint32_t cv[8],
                      uint8_t out[64], size_t outblocks) {
 #if defined(IS_X86)
   const enum cpu_feature features = get_cpu_features();
-#if !defined(BLAKE3_NO_AVX512)
+#if defined(__unix__) && !defined(BLAKE3_NO_AVX512)
   if (features & AVX512VL) {
     blake3_xof_many_avx512(cv, block, block_len, counter, flags, out, outblocks);
     return;
diff --git a/c/blake3_impl.h b/c/blake3_impl.h
index 66a17079..abd75467 100644
--- a/c/blake3_impl.h
+++ b/c/blake3_impl.h
@@ -288,12 +288,14 @@ void blake3_hash_many_avx512(const uint8_t *const *inputs, size_t num_inputs,
                              uint8_t flags, uint8_t flags_start,
                              uint8_t flags_end, uint8_t *out);
 
+#if defined(__unix__)
 void blake3_xof_many_avx512(const uint32_t cv[8],
                             const uint8_t block[BLAKE3_BLOCK_LEN],
                             uint8_t block_len, uint64_t counter, uint8_t flags,
                             uint8_t* out, size_t outblocks);
 #endif
 #endif
+#endif
 
 #if BLAKE3_USE_NEON == 1
 void blake3_hash_many_neon(const uint8_t *const *inputs, size_t num_inputs,
diff --git a/src/ffi_avx512.rs b/src/ffi_avx512.rs
index d34e53c6..67947746 100644
--- a/src/ffi_avx512.rs
+++ b/src/ffi_avx512.rs
@@ -61,6 +61,7 @@ pub unsafe fn hash_many<const N: usize>(
 }
 
 // Unsafe because this may only be called on platforms supporting AVX-512.
+#[cfg(unix)]
 pub unsafe fn xof_many(
     cv: &CVWords,
     block: &[u8; BLOCK_LEN],
@@ -109,6 +110,7 @@ pub mod ffi {
             flags_end: u8,
             out: *mut u8,
         );
+        #[cfg(unix)]
         pub fn blake3_xof_many_avx512(
             cv: *const u32,
             block: *const u8,
@@ -141,6 +143,7 @@ mod test {
         crate::test::test_hash_many_fn(hash_many, hash_many);
     }
 
+    #[cfg(unix)]
     #[test]
     fn test_xof_many() {
         if !crate::platform::avx512_detected() {
diff --git a/src/platform.rs b/src/platform.rs
index 1858addc..6e4ae259 100644
--- a/src/platform.rs
+++ b/src/platform.rs
@@ -289,6 +289,7 @@ impl Platform {
         match self {
             // Safe because detect() checked for platform support.
             #[cfg(blake3_avx512_ffi)]
+            #[cfg(unix)]
             #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
             Platform::AVX512 => unsafe {
                 crate::avx512::xof_many(cv, block, block_len, counter, flags, out)