--- a/configure.in
+++ b/configure.in
@@ -426,17 +426,17 @@ MOZ_ARG_ENABLE_BOOL([rust],
                     [  --enable-rust           Include rust language sources],
                     [MOZ_RUST=1],
                     [MOZ_RUST= ])
 if test -z "$RUSTC" -a -n "$MOZ_RUST"; then
   AC_MSG_ERROR([Rust compiler not found.
     To compile rust language sources, you must have 'rustc' in your path.
     See http://www.rust-lang.org/ for more information.])
 fi
-if test -n "$MOZ_RUST" -a -z "$_RUSTC_MAJOR_VERSION" -o \
+if test -n "$MOZ_RUST" && test -z "$_RUSTC_MAJOR_VERSION" -o \
   "$_RUSTC_MAJOR_VERSION" -lt 1; then
   AC_MSG_ERROR([Rust compiler ${RUSTC_VERSION} is too old.
     To compile rust language sources please install at least
     version 1.0 of the 'rustc' toolchain and make sure it is
     first in your path.
     You can verify this by typing 'rustc --version'.])
 fi
 AC_SUBST(MOZ_RUST)