diff --git a/.appveyor.yml b/.appveyor.yml
index c3d575403cb..582b55f62db 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -36,7 +36,7 @@ install:
 build_script:
     - set RUSTFLAGS=-C debug-assertions
     # Build and install miri
-    - cargo build --release --all-features --all-targets
+    - cargo build --release --all-features --all-targets --locked
     - cargo install --all-features --force --path . --locked --offline
     # Get ourselves a MIR-full libstd, and use it henceforth
     - cargo miri setup
@@ -46,7 +46,7 @@ test_script:
     - set RUST_TEST_NOCAPTURE=1
     - set RUST_BACKTRACE=1
     # Test miri
-    - cargo test --release --all-features
+    - cargo test --release --all-features --locked
     # Test cargo integration
     - cd test-cargo-miri
     - '"C:\msys64\mingw64\bin\python3.exe" run-test.py'
diff --git a/travis.sh b/travis.sh
index 6f14be44ef0..af297129e82 100755
--- a/travis.sh
+++ b/travis.sh
@@ -12,13 +12,13 @@ export RUSTC_EXTRA_FLAGS="-D warnings"
 
 # Prepare
 echo "Build and install miri"
-./miri build --all-targets
-./miri install
+./miri build --all-targets --locked
+./miri install # implicitly locked
 echo
 
 # Test
 function run_tests {
-    ./miri test
+    ./miri test --locked
     # "miri test" has built the sysroot for us, now this should pass without
     # any interactive questions.
     test-cargo-miri/run-test.py