diff --git a/CMakeLists.txt b/CMakeLists.txt
index 845ddf0e..8e88d4df 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -342,7 +342,7 @@ elseif(SIZEOF_UNSIGNED_LONG EQUAL SIZEOF_SIZE_T)
   set(TIFF_SIZE_T "unsigned long")
   set(TIFF_SIZE_FORMAT "%lu")
 elseif(SIZEOF_UNSIGNED_LONG_LONG EQUAL SIZEOF_SIZE_T)
-  set(TIFF_SIZE_T "unsigned long")
+  set(TIFF_SIZE_T "unsigned long long")
   if (MINGW)
     set(TIFF_SIZE_FORMAT "%I64u")
   else()