diff --git a/src/bin/jpip/CMakeLists.txt b/src/bin/jpip/CMakeLists.txt
index 9404c111..821b2015 100644
--- a/src/bin/jpip/CMakeLists.txt
+++ b/src/bin/jpip/CMakeLists.txt
@@ -59,6 +59,14 @@ endforeach()
 # Build the two java clients:
 find_package(Java 1.5 COMPONENTS Development) # javac, jar
 
+# User can override this:
+if(NOT DEFINED JAVA_SOURCE_VERSION) 
+  set(JAVA_SOURCE_VERSION 1.5)
+endif()
+if(NOT DEFINED JAVA_TARGET_VERSION)
+  set(JAVA_TARGET_VERSION 1.5)
+endif()
+
 # Only build the java viewer if dev is found:
 if(Java_Development_FOUND AND Java_JAVAC_EXECUTABLE)
   set(jflags $ENV{JFLAGS})
@@ -97,6 +105,7 @@ if(Java_Development_FOUND AND Java_JAVAC_EXECUTABLE)
     add_custom_command(
       OUTPUT ${LIBRARY_OUTPUT_PATH}/opj_jpip_viewer.jar
       COMMAND ${Java_JAVAC_EXECUTABLE} ${jflags}
+      -source ${JAVA_SOURCE_VERSION} -target ${JAVA_TARGET_VERSION}
       -classpath ${APACHE_XERCES_JAR}
       ${java2_srcs} -d ${CMAKE_CURRENT_BINARY_DIR}/classes2
       COMMAND ${Java_JAR_EXECUTABLE} cfm ${LIBRARY_OUTPUT_PATH}/opj_jpip_viewer.jar
@@ -127,6 +136,7 @@ if(Java_Development_FOUND AND Java_JAVAC_EXECUTABLE)
     add_custom_command(
       OUTPUT ${LIBRARY_OUTPUT_PATH}/opj_jpip_viewer.jar
       COMMAND ${Java_JAVAC_EXECUTABLE} ${jflags}
+      -source ${JAVA_SOURCE_VERSION} -target ${JAVA_TARGET_VERSION}
       ${java1_srcs} -d ${CMAKE_CURRENT_BINARY_DIR}/classes1
       COMMAND ${Java_JAR_EXECUTABLE} cfm ${LIBRARY_OUTPUT_PATH}/opj_jpip_viewer.jar
       ${CMAKE_CURRENT_SOURCE_DIR}/opj_viewer/dist/manifest.txt -C