diff --git a/povray_wasm/build_ubuntu.sh b/povray_wasm/build_ubuntu.sh
index ff4f549..5d97e66 100644
--- a/povray_wasm/build_ubuntu.sh
+++ b/povray_wasm/build_ubuntu.sh
@@ -5,7 +5,7 @@ NAME="Matt McWilliams"
 
 BOOST_ROOT="/lib/x86_64-linux-gnu/"
 
-CFLAGS="-pthread -DBOOST_THREAD_USE_LIB -DBOOST_HAS_PTHREADS -s USE_BOOST_HEADERS=1"
+CFLAGS="-pthread -DBOOST_THREAD_USE_LIB -s USE_BOOST_HEADERS=1"
 LDFLAGS="$CFLAGS -s INITIAL_MEMORY=33554432" # 33554432 bytes = 32 MB
 CONFIG_ARGS=(
   --arch=x86_32           # use x86_32 to achieve minimal architectural optimization