diff --git a/test/internal_sys_mock.hpp b/test/internal_sys_mock.hpp
index 2225203..1171540 100644
--- a/test/internal_sys_mock.hpp
+++ b/test/internal_sys_mock.hpp
@@ -21,7 +21,7 @@
     MOCK_CONST_METHOD2(open, int(const char*, int));
     MOCK_CONST_METHOD1(close, int(int));
     MOCK_CONST_METHOD6(mmap, void*(void*, size_t, int, int, int, off_t));
-    MOCK_CONST_METHOD2(munmap, int(void*, size));
+    MOCK_CONST_METHOD2(munmap, int(void*, size_t));
     MOCK_CONST_METHOD0(getpagesize, int());
     MOCK_CONST_METHOD3(ioctl, int(int, unsigned long, void*));
 };