diff --git a/applications/jpip/util/CMakeLists.txt b/applications/jpip/util/CMakeLists.txt
index dbce6e48..a87e41d4 100644
--- a/applications/jpip/util/CMakeLists.txt
+++ b/applications/jpip/util/CMakeLists.txt
@@ -57,6 +57,14 @@ ENDFOREACH(exe)
 # 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})
@@ -70,6 +78,7 @@ if(Java_Development_FOUND AND Java_JAVAC_EXECUTABLE)
   ADD_CUSTOM_COMMAND(
     OUTPUT ${LIBRARY_OUTPUT_PATH}/opj_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_viewer.jar
     ${CMAKE_CURRENT_SOURCE_DIR}/opj_viewer/dist/manifest.txt -C
@@ -124,6 +133,7 @@ if(Java_Development_FOUND AND Java_JAVAC_EXECUTABLE)
     ADD_CUSTOM_COMMAND(
       OUTPUT ${LIBRARY_OUTPUT_PATH}/opj_viewer_xerces.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_viewer_xerces.jar