diff --git a/.cirrus.yml b/.cirrus.yml
index 178f5b24690c5..e3f777b52907f 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -10,6 +10,7 @@ task:
     - rustup default stable
   test_script:
     - . $HOME/.cargo/env
+    - LIBC_CI=1 sh ci/run.sh x86_64-unknown-freebsd
     - sh ci/run.sh x86_64-unknown-freebsd
     
 task:
@@ -24,4 +25,5 @@ task:
     - rustup default nightly
   test_script:
     - . $HOME/.cargo/env
+    - LIBC_CI=1 sh ci/run.sh x86_64-unknown-freebsd
     - sh ci/run.sh x86_64-unknown-freebsd
diff --git a/Cargo.toml b/Cargo.toml
index c6e1b98c21aee..a39ab2945ceb1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "libc"
-version = "0.2.61"
+version = "0.2.62"
 authors = ["The Rust Project Developers"]
 license = "MIT OR Apache-2.0"
 readme = "README.md"
diff --git a/build.rs b/build.rs
index f355447a672c6..efc95b6627493 100644
--- a/build.rs
+++ b/build.rs
@@ -7,6 +7,8 @@ fn main() {
         rustc_minor_version().expect("Failed to get rustc version");
     let rustc_dep_of_std = env::var("CARGO_FEATURE_RUSTC_DEP_OF_STD").is_ok();
     let align_cargo_feature = env::var("CARGO_FEATURE_ALIGN").is_ok();
+    #[allow(unused)]
+    let libc_ci = env::var("LIBC_CI").is_ok();
 
     if env::var("CARGO_FEATURE_USE_STD").is_ok() {
         println!(
@@ -15,16 +17,15 @@ fn main() {
         );
     }
 
-    if env::var("LIBC_CI").is_ok() {
-        if let Some(11) = which_freebsd() {
-            println!("cargo:rustc-cfg=freebsd11");
-        }
-        if let Some(12) = which_freebsd() {
-            println!("cargo:rustc-cfg=freebsd12");
-        }
-        if let Some(13) = which_freebsd() {
-            println!("cargo:rustc-cfg=freebsd13");
-        }
+    // The ABI of libc is backward compatible with FreeBSD 11.
+    //
+    // On CI, we detect the actual FreeBSD version and match its ABI exactly,
+    // running tests to ensure that the ABI is correct.
+    match which_freebsd() {
+        Some(11) if libc_ci => println!("cargo:rustc-cfg=freebsd11"),
+        Some(12) if libc_ci => println!("cargo:rustc-cfg=freebsd12"),
+        Some(13) if libc_ci => println!("cargo:rustc-cfg=freebsd13"),
+        Some(_) | None => println!("cargo:rustc-cfg=freebsd11"),
     }
 
     // Rust >= 1.15 supports private module use:
diff --git a/ci/azure.yml b/ci/azure.yml
index 04d12dae8f316..4526361aefbe6 100644
--- a/ci/azure.yml
+++ b/ci/azure.yml
@@ -15,7 +15,7 @@ jobs:
       vmImage: ubuntu-16.04
     steps:
       - template: azure-install-rust.yml
-      - bash: sh ./ci/run-docker.sh $TARGET
+      - bash: LIBC_CI=1 sh ./ci/run-docker.sh $TARGET
         displayName: Execute run-docker.sh
     strategy:
       matrix:
@@ -30,7 +30,7 @@ jobs:
       vmImage: ubuntu-16.04
     steps:
       - template: azure-install-rust.yml
-      - bash: sh ./ci/run-docker.sh $TARGET
+      - bash: LIBC_CI=1 sh ./ci/run-docker.sh $TARGET
         displayName: Execute run-docker.sh
     strategy:
       matrix:
@@ -88,7 +88,7 @@ jobs:
       vmImage: macos-10.14
     steps:
       - template: azure-install-rust.yml
-      - bash: sh ./ci/run.sh $TARGET
+      - bash: LIBC_CI=1 sh ./ci/run.sh $TARGET
         displayName: Execute run.sh
     strategy:
       matrix:
@@ -100,7 +100,7 @@ jobs:
       vmImage: macos-10.13
     steps:
       - template: azure-install-rust.yml
-      - bash: sh ./ci/run.sh $TARGET
+      - bash: LIBC_CI=1 sh ./ci/run.sh $TARGET
         displayName: Execute run.sh
     strategy:
       matrix:
@@ -112,7 +112,7 @@ jobs:
       vmImage: vs2017-win2016
     steps:
       - template: azure-install-rust.yml
-      - bash: sh ./ci/run.sh $TARGET
+      - bash: LIBC_CI=1 sh ./ci/run.sh $TARGET
         displayName: Execute run.sh
     strategy:
       matrix:
diff --git a/ci/dox.sh b/ci/dox.sh
index 49abd546001c8..febe18b35b836 100644
--- a/ci/dox.sh
+++ b/ci/dox.sh
@@ -47,6 +47,9 @@ while read -r target; do
 
     rustup target add "${target}" || true
 
+    # Enable extra configuration flags:
+    export RUSTDOCFLAGS="--cfg freebsd11"
+
     # If cargo doc fails, then try xargo:
     if ! cargo doc --target "${target}" \
              --no-default-features  --features extra_traits ; then
diff --git a/ci/run-docker.sh b/ci/run-docker.sh
index 5fd00614462dc..3c0736a265f7b 100755
--- a/ci/run-docker.sh
+++ b/ci/run-docker.sh
@@ -23,6 +23,7 @@ run() {
     docker run \
       --rm \
       --user "$(id -u)":"$(id -g)" \
+      --env LIBC_CI \
       --env CARGO_HOME=/cargo \
       --env CARGO_TARGET_DIR=/checkout/target \
       --volume "$(dirname "$(dirname "$(command -v cargo)")")":/cargo \
diff --git a/ci/run.sh b/ci/run.sh
index 8c56979ed657f..6f2ca11fe4090 100755
--- a/ci/run.sh
+++ b/ci/run.sh
@@ -87,8 +87,6 @@ if [ "$TARGET" = "x86_64-unknown-linux-gnux32" ]; then
   opt="--release"
 fi
 
-export LIBC_CI=1
-
 cargo test -vv $opt --no-default-features --manifest-path libc-test/Cargo.toml \
       --target "${TARGET}"
 
diff --git a/src/unix/bsd/freebsdlike/freebsd/mod.rs b/src/unix/bsd/freebsdlike/freebsd/mod.rs
index c178b91b9408e..fea680d2af40c 100644
--- a/src/unix/bsd/freebsdlike/freebsd/mod.rs
+++ b/src/unix/bsd/freebsdlike/freebsd/mod.rs
@@ -1334,9 +1334,11 @@ cfg_if! {
     } else if #[cfg(freebsd13)] {
         mod freebsd12;
         pub use self::freebsd12::*;
-    } else {
+    } else if #[cfg(freebsd11)] {
         mod freebsd11;
         pub use self::freebsd11::*;
+    } else {
+        // Unknown freebsd version
     }
 }