diff --git a/Tests/CMakeTests/FileDownloadTest.cmake.in b/Tests/CMakeTests/FileDownloadTest.cmake.in
index 69d9a14c4b..e0ce99ab8c 100644
--- a/Tests/CMakeTests/FileDownloadTest.cmake.in
+++ b/Tests/CMakeTests/FileDownloadTest.cmake.in
@@ -136,6 +136,9 @@ __reportIfWrongStatus("${status}" 0)
 # Print status because we check its message too
 message(STATUS "${status}")
 
+# do not use proxy for lookup of invalid site (DNS failure by proxy looks
+# different than DNS failure without proxy)
+set(ENV{no_proxy} "$ENV{no_proxy},badhostname.invalid")
 message(STATUS "FileDownload:11")
 file(DOWNLOAD
   badhostname.invalid
diff --git a/Tests/RunCMake/ctest_submit/CTestConfig.cmake.in b/Tests/RunCMake/ctest_submit/CTestConfig.cmake.in
index 140e4be358..c35397cb83 100644
--- a/Tests/RunCMake/ctest_submit/CTestConfig.cmake.in
+++ b/Tests/RunCMake/ctest_submit/CTestConfig.cmake.in
@@ -3,3 +3,7 @@
 # so that any ctest_submit calls fail with an error message.
 set(CTEST_DROP_METHOD "@CASE_DROP_METHOD@")
 set(CTEST_DROP_SITE "@CASE_DROP_SITE@")
+
+# do not use proxy for lookup of invalid site (DNS failure by proxy looks
+# different than DNS failure without proxy)
+set(ENV{no_proxy} "$ENV{no_proxy},@CASE_DROP_SITE@")