diff --git a/.travis.yml b/.travis.yml
index 3bac944..11f5c77 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -94,6 +94,8 @@
       osx_image: xcode8.3
       rust: nightly
     # not available on stable
+    # without --release the build fails
+    # see https://github.com/rust-lang/rust/issues/45417
     - env: TARGET=x86_64-unknown-linux-gnux32 OPT="--release"
       rust: nightly
 
diff --git a/ci/run.sh b/ci/run.sh
index 65d716e..420542a 100755
--- a/ci/run.sh
+++ b/ci/run.sh
@@ -69,6 +69,7 @@
 fi
 
 # FIXME: x86_64-unknown-linux-gnux32 fail to compile wihout --release
+# See https://github.com/rust-lang/rust/issues/45417
 opt=
 if [ "$TARGET" = "x86_64-unknown-linux-gnux32" ]; then
   opt="--release"