diff --git a/core/combo/javac.mk b/core/combo/javac.mk
index f8c99fb..74490fd 100644
--- a/core/combo/javac.mk
+++ b/core/combo/javac.mk
@@ -6,13 +6,21 @@
 #
 # Outputs:
 #   COMMON_JAVAC -- Java compiler command with common arguments
+#
+
+ifeq ($(EXPERIMENTAL_USE_JAVA7_OPENJDK),)
+common_flags := -target 1.5 -Xmaxerrs 9999999
+else
+common_flags := -Xmaxerrs 9999999
+endif
+
 
 # Whatever compiler is on this system.
 ifeq ($(BUILD_OS), windows)
     COMMON_JAVAC := development/host/windows/prebuilt/javawrap.exe -J-Xmx256m \
-        -target 1.5 -Xmaxerrs 9999999
+        $(common_flags)
 else
-    COMMON_JAVAC := javac -J-Xmx512M -target 1.5 -Xmaxerrs 9999999
+    COMMON_JAVAC := javac -J-Xmx512M $(common_flags)
 endif
 
 # Eclipse.
@@ -22,14 +30,6 @@
     $(info CUSTOM_JAVA_COMPILER=eclipse)
 endif
 
-# OpenJDK.
-ifeq ($(CUSTOM_JAVA_COMPILER), openjdk)
-    # We set the VM options (like -Xmx) in the javac script.
-    COMMON_JAVAC := prebuilt/common/openjdk/bin/javac -target 1.5 \
-        -Xmaxerrs 9999999
-    $(info CUSTOM_JAVA_COMPILER=openjdk)
-endif
-   
 HOST_JAVAC ?= $(COMMON_JAVAC)
 TARGET_JAVAC ?= $(COMMON_JAVAC)
     
diff --git a/core/main.mk b/core/main.mk
index eac2a01..b49b969 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -140,7 +140,18 @@
 $(error Directory names containing spaces not supported)
 endif
 
-# Check for the corrent jdk
+# Check for the current jdk
+ifneq ($(EXPERIMENTAL_USE_JAVA7_OPENJDK),)
+# The user asked for java7 openjdk, so check that the host
+# java version is really openjdk
+ifeq ($(shell java -version 2>&1 | grep -i openjdk),)
+$(info ************************************************************)
+$(info You asked for an OpenJDK 7 build but your version is)
+$(info $(shell java -version 2>&1 | head -n 2).)
+$(info ************************************************************)
+$(error stop)
+endif # java version is not OpenJdk
+else # if EXPERIMENTAL_USE_JAVA7_OPENJDK
 ifneq ($(shell java -version 2>&1 | grep -i openjdk),)
 $(info ************************************************************)
 $(info You are attempting to build with an unsupported JDK.)
@@ -150,17 +161,30 @@
 $(info $(space)$(space)$(space)$(space)https://source.android.com/source/download.html)
 $(info ************************************************************)
 $(error stop)
-endif
+endif # java version is not Sun Oracle JDK
+endif # if EXPERIMENTAL_USE_JAVA7_OPENJDK
 
-# Check for the correct version of java
+# Check for the correct version of java, should be 1.7 if
+# EXPERIMENTAL_USE_JAVA7_OPENJDK is set, 1.6 otherwise.
+ifneq ($(EXPERIMENTAL_USE_JAVA7_OPENJDK),)
+required_version := "OpenJDK 1.7"
+required_javac_version := "1.7"
+java_version := $(shell java -version 2>&1 | head -n 1 | grep '^java .*[ "]1\.7[\. "$$]')
+javac_version := $(shell javac -version 2>&1 | head -n 1 | grep '[ "]1\.7[\. "$$]')
+else # if EXPERIMENTAL_USE_JAVA7_OPENJDK
+required_version := "JavaSE 1.6"
+required_javac_version := "1.6"
 java_version := $(shell java -version 2>&1 | head -n 1 | grep '^java .*[ "]1\.6[\. "$$]')
+javac_version := $(shell javac -version 2>&1 | head -n 1 | grep '[ "]1\.6[\. "$$]')
+endif # if EXPERIMENTAL_USE_JAVA7_OPENJDK
+
 ifeq ($(strip $(java_version)),)
 $(info ************************************************************)
 $(info You are attempting to build with the incorrect version)
 $(info of java.)
 $(info $(space))
 $(info Your version is: $(shell java -version 2>&1 | head -n 1).)
-$(info The correct version is: Java SE 1.6.)
+$(info The required version is: $(required_version))
 $(info $(space))
 $(info Please follow the machine setup instructions at)
 $(info $(space)$(space)$(space)$(space)https://source.android.com/source/download.html)
@@ -169,14 +193,13 @@
 endif
 
 # Check for the correct version of javac
-javac_version := $(shell javac -version 2>&1 | head -n 1 | grep '[ "]1\.6[\. "$$]')
 ifeq ($(strip $(javac_version)),)
 $(info ************************************************************)
 $(info You are attempting to build with the incorrect version)
 $(info of javac.)
 $(info $(space))
 $(info Your version is: $(shell javac -version 2>&1 | head -n 1).)
-$(info The correct version is: 1.6.)
+$(info The required version is: $(required_javac_version))
 $(info $(space))
 $(info Please follow the machine setup instructions at)
 $(info $(space)$(space)$(space)$(space)https://source.android.com/source/download.html)