diff --git a/lib/capnp_c.h b/lib/capnp_c.h
index edbc43e..df6604c 100644
--- a/lib/capnp_c.h
+++ b/lib/capnp_c.h
@@ -24,11 +24,6 @@
 typedef intmax_t ssize_t;
 #endif
 
-// Macro UNUSED(x) silences compiler warnings about unused parameter or variable `x`.
-#ifndef UNUSED
-#define UNUSED(x) (void)(x)
-#endif
-
 // Cross-platform macro ALIGNED_(x) aligns a struct by `x` bytes.
 #ifdef _MSC_VER
 #define ALIGNED_(x) __declspec(align(x))