--- old/make/bsd/makefiles/rules.make	2020-01-16 16:56:25.483627526 +0300
+++ new/make/bsd/makefiles/rules.make	2020-01-16 16:56:25.435629075 +0300
@@ -126,8 +126,14 @@
 RUN.JAR$(MAKE_VERBOSE) += >/dev/null
 
 # Settings for javac
+ifeq ($(ENABLE_JFR), true)
+# JFR source code is consciously left as close as possible to later versions of JDK. hence need at least lambda support
 BOOT_SOURCE_LANGUAGE_VERSION = 8
 BOOT_TARGET_CLASS_VERSION = 8
+else
+BOOT_SOURCE_LANGUAGE_VERSION = 7
+BOOT_TARGET_CLASS_VERSION = 7
+endif
 JAVAC_FLAGS = -g -encoding ascii
 BOOTSTRAP_JAVAC_FLAGS = $(JAVAC_FLAGS) -source $(BOOT_SOURCE_LANGUAGE_VERSION) -target $(BOOT_TARGET_CLASS_VERSION)