diff --git a/scripts/cmake/vcpkg_download_distfile.cmake b/scripts/cmake/vcpkg_download_distfile.cmake
index 208871e3e3..1b06d7b5ba 100644
--- a/scripts/cmake/vcpkg_download_distfile.cmake
+++ b/scripts/cmake/vcpkg_download_distfile.cmake
@@ -80,6 +80,13 @@ function(vcpkg_download_distfile VAR)
             message(FATAL_ERROR "vcpkg_download_distfile must not be passed both SHA512 and SKIP_SHA512.")
         endif()
     endif()
+    if(vcpkg_download_distfile_SHA512 STREQUAL "0")
+        string(REPEAT "0" 128 vcpkg_download_distfile_SHA512)
+    endif()
+    string(LENGTH "${vcpkg_download_distfile_SHA512}" vcpkg_download_distfile_SHA512_length)
+    if(NOT vcpkg_download_distfile_SHA512_length EQUAL "128")
+        message(FATAL_ERROR "Invalid SHA512: ${vcpkg_download_distfile_SHA512}. If you do not know the file's SHA512, set this to \"0\".")
+    endif()
 
     set(downloaded_file_path ${DOWNLOADS}/${vcpkg_download_distfile_FILENAME})
     set(download_file_path_part "${DOWNLOADS}/temp/${vcpkg_download_distfile_FILENAME}")