diff --git a/src/mm_context.h b/src/mm_context.h
index 7952a843..691a3b70 100644
--- a/src/mm_context.h
+++ b/src/mm_context.h
@@ -7,9 +7,11 @@
  * cooperative multitasking engine.
 */
 
+typedef void (*mm_context_callback_t)(void*);
+
 void *mm_context_alloc(size_t);
 void  mm_context_free(void*);
-void  mm_context_create(void*, void (*)(void*), void*);
+void  mm_context_create(void*, mm_context_callback_t, void*);
 void  mm_context_swap(void*, void*);
 
 #endif