--- a/make/autoconf/boot-jdk.m4	Tue Dec 05 13:32:07 2017 +0100
+++ b/make/autoconf/boot-jdk.m4	Wed Dec 06 14:13:50 2017 +0100
@@ -354,7 +354,7 @@
   AC_MSG_CHECKING([flags for boot jdk java command] )
 
   # Disable special log output when a debug build is used as Boot JDK...
-  ADD_JVM_ARG_IF_OK([-XX:-PrintVMOptions -XX:+UnlockDiagnosticVMOptions -XX:-LogVMOutput],boot_jdk_jvmargs,[$JAVA])
+  ADD_JVM_ARG_IF_OK([-XX:-PrintVMOptions -XX:-UnlockDiagnosticVMOptions -XX:-LogVMOutput],boot_jdk_jvmargs,[$JAVA])
 
   # Force en-US environment
   ADD_JVM_ARG_IF_OK([-Duser.language=en -Duser.country=US],boot_jdk_jvmargs,[$JAVA])