diff --git a/ostd/coroutine.hh b/ostd/coroutine.hh
index d88f8fe..7655b2d 100644
--- a/ostd/coroutine.hh
+++ b/ostd/coroutine.hh
@@ -17,9 +17,10 @@
 #include <optional>
 
 #include "ostd/types.hh"
-#include "ostd/platform.hh"
 #include "ostd/range.hh"
 
+#include "ostd/internal/context.hh"
+
 namespace ostd {
 
 constexpr size_t COROUTINE_DEFAULT_STACK_SIZE = SIGSTKSZ;
@@ -35,96 +36,6 @@ template<typename T>
 struct coroutine_range;
 
 namespace detail {
-    /* from boost.fcontext */
-    using fcontext_t = void *;
-
-    struct transfer_t {
-        fcontext_t ctx;
-        void *data;
-    };
-
-    extern "C" OSTD_EXPORT
-    transfer_t OSTD_CDECL ostd_jump_fcontext(
-        fcontext_t const to, void *vp
-    );
-
-    extern "C" OSTD_EXPORT
-    fcontext_t OSTD_CDECL ostd_make_fcontext(
-        void *sp, size_t size, void (*fn)(transfer_t)
-    );
-
-    extern "C" OSTD_EXPORT
-    transfer_t OSTD_CDECL ostd_ontop_fcontext(
-        fcontext_t const to, void *vp, transfer_t (*fn)(transfer_t)
-    );
-
-    struct coroutine_context {
-    protected:
-        struct forced_unwind {
-            fcontext_t ctx;
-            forced_unwind(fcontext_t c): ctx(c) {}
-        };
-
-        coroutine_context() {}
-
-        coroutine_context(coroutine_context const &) = delete;
-        coroutine_context(coroutine_context &&c):
-            p_stack(std::move(c.p_stack)), p_coro(c.p_coro), p_orig(c.p_orig),
-            p_except(std::move(c.p_except))
-        {
-            c.p_coro = c.p_orig = nullptr;
-        }
-
-        coroutine_context &operator=(coroutine_context const &) = delete;
-        coroutine_context &operator=(coroutine_context &&c) {
-            swap(c);
-            return *this;
-        }
-
-        void call() {
-            coro_jump();
-            if (p_except) {
-                std::rethrow_exception(std::move(p_except));
-            }
-        }
-
-        void unwind() {
-            ostd_ontop_fcontext(
-                std::exchange(p_coro, nullptr), nullptr,
-                [](transfer_t t) -> transfer_t {
-                    throw forced_unwind{t.ctx};
-                }
-            );
-        }
-
-        void coro_jump() {
-            p_coro = ostd_jump_fcontext(p_coro, this).ctx;
-        }
-
-        void yield_jump() {
-            p_orig = ostd_jump_fcontext(p_orig, nullptr).ctx;
-        }
-
-        void swap(coroutine_context &other) noexcept {
-            using std::swap;
-            swap(p_stack, other.p_stack);
-            swap(p_coro, other.p_coro);
-            swap(p_orig, other.p_orig);
-            swap(p_except, other.p_except);
-        }
-
-        void make_context(size_t ss, void (*callp)(transfer_t)) {
-            p_stack = std::unique_ptr<byte[]>{new byte[ss]};
-            p_coro = ostd_make_fcontext(p_stack.get() + ss, ss, callp);
-        }
-
-        /* TODO: new'ing the stack is sub-optimal */
-        std::unique_ptr<byte[]> p_stack;
-        fcontext_t p_coro;
-        fcontext_t p_orig;
-        std::exception_ptr p_except;
-    };
-
     /* like reference_wrapper but for any value */
     template<typename T>
     struct arg_wrapper {
diff --git a/ostd/internal/context.hh b/ostd/internal/context.hh
new file mode 100644
index 0000000..49757a0
--- /dev/null
+++ b/ostd/internal/context.hh
@@ -0,0 +1,112 @@
+/* Context switching and stack allocation.
+ *
+ * This file is part of OctaSTD. See COPYING.md for futher information.
+ */
+
+#ifndef OSTD_INTERNAL_CONTEXT_HH
+#define OSTD_INTERNAL_CONTEXT_HH
+
+#include <memory>
+#include <exception>
+
+#include "ostd/types.hh"
+#include "ostd/platform.hh"
+#include "ostd/internal/win32.hh"
+
+namespace ostd {
+namespace detail {
+
+/* from boost.fcontext */
+using fcontext_t = void *;
+
+struct transfer_t {
+    fcontext_t ctx;
+    void *data;
+};
+
+extern "C" OSTD_EXPORT
+transfer_t OSTD_CDECL ostd_jump_fcontext(
+    fcontext_t const to, void *vp
+);
+
+extern "C" OSTD_EXPORT
+fcontext_t OSTD_CDECL ostd_make_fcontext(
+    void *sp, size_t size, void (*fn)(transfer_t)
+);
+
+extern "C" OSTD_EXPORT
+transfer_t OSTD_CDECL ostd_ontop_fcontext(
+    fcontext_t const to, void *vp, transfer_t (*fn)(transfer_t)
+);
+
+struct coroutine_context {
+protected:
+    struct forced_unwind {
+        fcontext_t ctx;
+        forced_unwind(fcontext_t c): ctx(c) {}
+    };
+
+    coroutine_context() {}
+
+    coroutine_context(coroutine_context const &) = delete;
+    coroutine_context(coroutine_context &&c):
+        p_stack(std::move(c.p_stack)), p_coro(c.p_coro), p_orig(c.p_orig),
+        p_except(std::move(c.p_except))
+    {
+        c.p_coro = c.p_orig = nullptr;
+    }
+
+    coroutine_context &operator=(coroutine_context const &) = delete;
+    coroutine_context &operator=(coroutine_context &&c) {
+        swap(c);
+        return *this;
+    }
+
+    void call() {
+        coro_jump();
+        if (p_except) {
+            std::rethrow_exception(std::move(p_except));
+        }
+    }
+
+    void unwind() {
+        ostd_ontop_fcontext(
+            std::exchange(p_coro, nullptr), nullptr,
+            [](transfer_t t) -> transfer_t {
+                throw forced_unwind{t.ctx};
+            }
+        );
+    }
+
+    void coro_jump() {
+        p_coro = ostd_jump_fcontext(p_coro, this).ctx;
+    }
+
+    void yield_jump() {
+        p_orig = ostd_jump_fcontext(p_orig, nullptr).ctx;
+    }
+
+    void swap(coroutine_context &other) noexcept {
+        using std::swap;
+        swap(p_stack, other.p_stack);
+        swap(p_coro, other.p_coro);
+        swap(p_orig, other.p_orig);
+        swap(p_except, other.p_except);
+    }
+
+    void make_context(size_t ss, void (*callp)(transfer_t)) {
+        p_stack = std::unique_ptr<byte[]>{new byte[ss]};
+        p_coro = ostd_make_fcontext(p_stack.get() + ss, ss, callp);
+    }
+
+    /* TODO: new'ing the stack is sub-optimal */
+    std::unique_ptr<byte[]> p_stack;
+    fcontext_t p_coro;
+    fcontext_t p_orig;
+    std::exception_ptr p_except;
+};
+
+}
+}
+
+#endif