diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8c2e4ba04f..61ff1860fb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -404,7 +404,6 @@ if(SIZEOF_TIME_T STREQUAL "4")
 	message(WARNING " ** Warning, this system is unable to represent times past 2038\n"
 	                " ** It will behave incorrectly when handling valid RFC5280 dates")
 endif()
-add_definitions(-DSIZEOF_TIME_T=${SIZEOF_TIME_T})
 
 set(OPENSSL_LIBS ssl crypto ${PLATFORM_LIBS})
 set(LIBTLS_LIBS tls ${PLATFORM_LIBS})
diff --git a/include/compat/time.h b/include/compat/time.h
index 540807dd88..27485218fb 100644
--- a/include/compat/time.h
+++ b/include/compat/time.h
@@ -3,6 +3,14 @@
  * sys/time.h compatibility shim
  */
 
+#ifndef SIZEOF_TIME_T
+#ifdef SMALL_TIME_T
+#define SIZEOF_TIME_T 4
+#else
+#define SIZEOF_TIME_T 8
+#endif
+#endif
+
 #ifdef _MSC_VER
 #if _MSC_VER >= 1900
 #include <../ucrt/time.h>