diff --git a/build.gradle b/build.gradle
index 3096e0e..7cd0f09 100644
--- a/build.gradle
+++ b/build.gradle
@@ -22,13 +22,6 @@
 group = 'com.android'
 version = '1.0.6'
 
-def currentJvmVersion = org.gradle.api.JavaVersion.current()
-if (currentJvmVersion.getMajorVersion() != "8") {
-  throw new Exception("Unsupported java version '" + currentJvmVersion.toString() + "'. Please install java 8.\n" +
-"\n" +
-"If you have already installed java 8, you can instruct Gradle to use it by setting the environment variable JAVA_HOME equal to its file path.")
-}
-
 /*
  * With the build server you are given two env variables:
  * 1. The OUT_DIR is a temporary directory you can use to put things during the build.
@@ -85,7 +78,17 @@
     testCompile 'junit:junit:4.12'
 
     // tools.jar required for com.sun.javadoc
-    compile files(((URLClassLoader) ToolProvider.getSystemToolClassLoader()).getURLs())
+    def currentJvmVersion = org.gradle.api.JavaVersion.current()
+    def toolsJar;
+    if (currentJvmVersion.getMajorVersion() == "8") {
+        toolsJar = ((URLClassLoader) ToolProvider.getSystemToolClassLoader()).getURLs()
+    } else if (System.env.JAVA_TOOLS_JAR != null) {
+        toolsJar = System.env.JAVA_TOOLS_JAR
+    } else {
+        throw new Exception("If you are not using Java 8, JAVA_TOOLS_JAR env variable " +
+            "needs to be set to build Doclava")
+    }
+    compile files(toolsJar)
 }
 
 sourceSets {