diff -r cf8310446245 -r dbfac941197a src/jdk.compiler/share/classes/com/sun/tools/javac/file/Locations.java
--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/file/Locations.java	Mon Nov 06 13:10:43 2017 +0100
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/file/Locations.java	Mon Nov 06 14:10:39 2017 +0100
@@ -1371,7 +1371,8 @@
 
             private Pair<String,Path> inferModuleName(Path p) {
                 if (Files.isDirectory(p)) {
-                    if (Files.exists(p.resolve("module-info.class"))) {
+                    if (Files.exists(p.resolve("module-info.class")) ||
+                        Files.exists(p.resolve("module-info.sig"))) {
                         String name = p.getFileName().toString();
                         if (SourceVersion.isName(name))
                             return new Pair<>(name, p);