--- a/old-configure.in
+++ b/old-configure.in
@@ -9130,18 +9130,16 @@ RC=
 # Run the SpiderMonkey 'configure' script.
 dist=$MOZ_BUILD_ROOT/dist
 ac_configure_args="$_SUBDIR_CONFIG_ARGS"
 
 # --with-system-nspr will have been converted into the relevant $NSPR_CFLAGS
 # and $NSPR_LIBS.
 ac_configure_args="`echo $ac_configure_args | sed -e 's/--with-system-nspr\S* *//'`"
 
-ac_configure_args="$ac_configure_args --enable-threadsafe"
-
 if test "$_INTL_API" = no; then
     ac_configure_args="$ac_configure_args --without-intl-api"
 fi
 
 if test "$BUILD_CTYPES"; then
     # Build js-ctypes on the platforms we can.
     ac_configure_args="$ac_configure_args --enable-ctypes"
 fi

--- a/testing/mozharness/scripts/spidermonkey/build.shell
+++ b/testing/mozharness/scripts/spidermonkey/build.shell
@@ -1,9 +1,9 @@
 #!/bin/sh
 
 set -e
 set -x
 
 [ -d $ANALYZED_OBJDIR ] || mkdir $ANALYZED_OBJDIR
 cd $ANALYZED_OBJDIR
-$SOURCE/js/src/configure --enable-debug --enable-optimize --enable-stdcxx-compat --enable-ctypes --enable-exact-rooting --enable-gcgenerational --enable-threadsafe --with-system-nspr
+$SOURCE/js/src/configure --enable-debug --enable-optimize --enable-stdcxx-compat --enable-ctypes --enable-exact-rooting --enable-gcgenerational --with-system-nspr
 make -j12 -s