diff --git a/src/runtime/java/Makefile b/src/runtime/java/Makefile
index ce185e044..8310a5720 100644
--- a/src/runtime/java/Makefile
+++ b/src/runtime/java/Makefile
@@ -2,8 +2,9 @@ C_SOURCES = jpgf.c jsg.c jni_utils.c
 JAVA_SOURCES = $(wildcard org/grammaticalframework/pgf/*.java) \
                $(wildcard org/grammaticalframework/sg/*.java)
 
-JNI_PATH = /usr/lib/jvm/default-java/include
-#JNI_PATH = /System/Library/Frameworks/JavaVM.framework/Versions/A/Headers/
+JNI_PATH = $(if $(wildcard /usr/lib/jvm/default-java/include/.*), /usr/lib/jvm/default-java/include, \
+           $(if $(wildcard /System/Library/Frameworks/JavaVM.framework/Versions/A/Headers/.*), /System/Library/Frameworks/JavaVM.framework/Versions/A/Headers, \
+           $(error No JNI headers found)))
 INSTALL_PATH = /usr/local/lib
 
 LIBTOOL = $(if $(shell command -v glibtool 2>/dev/null), glibtool --tag=CC, libtool)