diff --git a/projects/clang/build b/projects/clang/build
index 825b21e2e234131244464044539c15caa57380bf..d95e9af8961dc7820cadc7c74bd79c7c74bca15d 100644
--- a/projects/clang/build
+++ b/projects/clang/build
@@ -40,7 +40,10 @@ cd llvm
 export LLVM_HOME=$(pwd)
 mkdir build
 cd build
-cmake .. -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=$distdir -DCMAKE_BUILD_TYPE:STRING=Release $LLVM_HOME
+cmake .. -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=$distdir \
+                             -DCMAKE_BUILD_TYPE:STRING=Release \
+     [% IF c("var/rlbox") -%]-DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=WebAssembly \[% END -%]
+                             $LLVM_HOME
 make -j[% c("buildconf/num_procs") %]
 make install
 cd /var/tmp/dist
diff --git a/rbm.conf b/rbm.conf
index 73c617b1e79423e4dd4ad7691ea82ff58cb9184e..213971e2f02fe39f7372462190bec8be1e76ceab 100644
--- a/rbm.conf
+++ b/rbm.conf
@@ -262,6 +262,8 @@ targets:
     var:
       linux-x86_64: 1
       osname: linux-x86_64
+      # We only support RLBox on the nightly channel and x86_64 for now
+      rlbox: '[% c("var/nightly") %]'
   linux-i686:
     arch: i686
     var: