diff --git a/java/java.go b/java/java.go
index 4b48a15..3167512 100644
--- a/java/java.go
+++ b/java/java.go
@@ -1187,18 +1187,6 @@
 	// javaVersion flag.
 	flags.javaVersion = getJavaVersion(ctx, String(j.properties.Java_version), sdkContext(j))
 
-	// javac flags.
-	javacFlags := j.properties.Javacflags
-	if flags.javaVersion.usesJavaModules() {
-		javacFlags = append(javacFlags, j.properties.Openjdk9.Javacflags...)
-	}
-	if ctx.Config().MinimizeJavaDebugInfo() && !ctx.Host() {
-		// For non-host binaries, override the -g flag passed globally to remove
-		// local variable debug info to reduce disk and memory usage.
-		javacFlags = append(javacFlags, "-g:source,lines")
-	}
-	javacFlags = append(javacFlags, "-Xlint:-dep-ann")
-
 	if ctx.Config().RunErrorProne() {
 		if config.ErrorProneClasspath == nil {
 			ctx.ModuleErrorf("cannot build with Error Prone, missing external/error_prone?")
@@ -1249,24 +1237,42 @@
 		}
 	}
 
-	if j.properties.Patch_module != nil && flags.javaVersion.usesJavaModules() {
-		// Manually specify build directory in case it is not under the repo root.
-		// (javac doesn't seem to expand into symbolc links when searching for patch-module targets, so
-		// just adding a symlink under the root doesn't help.)
-		patchPaths := ".:" + ctx.Config().BuildDir()
-		classPath := flags.classpath.FormJavaClassPath("")
-		if classPath != "" {
-			patchPaths += ":" + classPath
-		}
-		javacFlags = append(javacFlags, "--patch-module="+String(j.properties.Patch_module)+"="+patchPaths)
-	}
-
 	// systemModules
 	flags.systemModules = deps.systemModules
 
 	// aidl flags.
 	flags.aidlFlags, flags.aidlDeps = j.aidlFlags(ctx, deps.aidlPreprocess, deps.aidlIncludeDirs)
 
+	return flags
+}
+
+func (j *Module) collectJavacFlags(ctx android.ModuleContext, flags javaBuilderFlags) javaBuilderFlags {
+	// javac flags.
+	javacFlags := j.properties.Javacflags
+
+	if ctx.Config().MinimizeJavaDebugInfo() && !ctx.Host() {
+		// For non-host binaries, override the -g flag passed globally to remove
+		// local variable debug info to reduce disk and memory usage.
+		javacFlags = append(javacFlags, "-g:source,lines")
+	}
+	javacFlags = append(javacFlags, "-Xlint:-dep-ann")
+
+	if flags.javaVersion.usesJavaModules() {
+		javacFlags = append(javacFlags, j.properties.Openjdk9.Javacflags...)
+
+		if j.properties.Patch_module != nil {
+			// Manually specify build directory in case it is not under the repo root.
+			// (javac doesn't seem to expand into symbolc links when searching for patch-module targets, so
+			// just adding a symlink under the root doesn't help.)
+			patchPaths := ".:" + ctx.Config().BuildDir()
+			classPath := flags.classpath.FormJavaClassPath("")
+			if classPath != "" {
+				patchPaths += ":" + classPath
+			}
+			javacFlags = append(javacFlags, "--patch-module="+String(j.properties.Patch_module)+"="+patchPaths)
+		}
+	}
+
 	if len(javacFlags) > 0 {
 		// optimization.
 		ctx.Variable(pctx, "javacFlags", strings.Join(javacFlags, " "))
@@ -1297,6 +1303,8 @@
 
 	srcFiles = j.genSources(ctx, srcFiles, flags)
 
+	flags = j.collectJavacFlags(ctx, flags)
+
 	srcJars := srcFiles.FilterByExt(".srcjar")
 	srcJars = append(srcJars, deps.srcJars...)
 	if aaptSrcJar != nil {