diff --git a/CMakeLists.txt b/CMakeLists.txt
index 363c041f..ae054b77 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -275,7 +275,11 @@ check_type_size("ssize_t" SIZEOF_SSIZE_T)
 if(SIZEOF_SSIZE_T STREQUAL "")
   # ssize_t is a signed type in POSIX storing at least -1.
   # Set it to "int" to match the behavior of AC_TYPE_SSIZE_T (autotools).
-  set(ssize_t int)
+  if(WIN32 AND CMAKE_SIZEOF_VOID_P EQUAL 8)
+    set(ssize_t int64_t)
+  else()
+    set(ssize_t int)
+  endif()
 endif()
 # AC_TYPE_UINT8_T
 # AC_TYPE_UINT16_T