diff --git a/.travis.yml b/.travis.yml
index 76ca5bb..41c5944 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,6 +4,7 @@ rust:
   - stable
   - beta
   - nightly
+os: linux
 
 # always test things that aren't pushes (like PRs)
 # never test tags or pushes to non-master branches (wait for PR)
@@ -16,7 +17,7 @@ before_script:
      docker run -d -e GREENMAIL_OPTS='-Dgreenmail.setup.test.all -Dgreenmail.hostname=0.0.0.0 -Dgreenmail.auth.disabled -Dgreenmail.verbose' -p 3025:3025 -p 3110:3110 -p 3143:3143 -p 3465:3465 -p 3993:3993 -p 3995:3995 greenmail/standalone:1.5.9;
    fi
 
-# an entry in stage=test will be generated for each rust/os combination.
+# an entry in stage=test will be generated for each rust version.
 # each entry will run these commands.
 script:
   - cargo test --examples
@@ -30,7 +31,6 @@ jobs:
       stage: check # do a pre-screen to make sure this is even worth testing
       script: cargo check --all-targets
       rust: stable
-      os: linux
       # <1.24 doesn't work because of lazy-static 1.2.0
       # <1.26.2 doesn't work because of nom 4.1.1
     - <<: *check # also test oldest known-good stable
@@ -51,7 +51,6 @@ jobs:
           packages:
             - libssl-dev
       rust: stable
-      os: linux
     - <<: *integration
       rust: beta
     - <<: *integration
@@ -59,25 +58,21 @@ jobs:
     - stage: lint # we lint on beta to future-proof
       name: "Rust: beta, rustfmt"
       rust: beta
-      os: linux
       script:
         - rustup component add rustfmt-preview
         - cargo fmt -v -- --check
     - name: "Rust: nightly, rustfmt" # and on nightly with allow_fail
       rust: nightly
-      os: linux
       script:
         - rustup component add rustfmt-preview
         - cargo fmt -v -- --check
     - name: "Rust: beta, clippy"
       rust: beta
-      os: linux
       script:
         - rustup component add clippy-preview
         - touch ./src/lib.rs && cargo clippy -- -D warnings
     - name: "Rust: nightly, clippy"
       rust: nightly
-      os: linux
       script:
         - rustup component add clippy-preview
         - touch ./src/lib.rs && cargo clippy -- -D warnings