diff --git a/ci/pipelines-ci.yml b/ci/pipelines-ci.yml
index b32c5b68..438608e5 100644
--- a/ci/pipelines-ci.yml
+++ b/ci/pipelines-ci.yml
@@ -54,7 +54,11 @@ stages:
               # additional native dependencies (included in `linuxPrestep`) and
               # adds too much a hassle for other platforms, especially
               # Windows + MSVC.
-              echo '##vso[task.setvariable variable=test_build_flags]$(test_build_flags) --features testing'
+              #
+              # However, you can't use `--feature` when testing a whole
+              # workspace (rust-lang/cargo#6195). So we use `--all-features`
+              # instead.
+              echo '##vso[task.setvariable variable=test_build_flags]$(test_build_flags) --all-features'
           MacOS:
             vmImage: macOS-10.13
             prepareScript: ""