diff --git a/make/src/classes/build/tools/jigsaw/GenGraphs.java b/make/src/classes/build/tools/jigsaw/GenGraphs.java
--- a/make/src/classes/build/tools/jigsaw/GenGraphs.java
+++ b/make/src/classes/build/tools/jigsaw/GenGraphs.java
@@ -214,13 +214,13 @@

            // same ranks
            ranks.stream()
- .forEach(group -> out.format("{rank=same %s}%n",
- descriptors.stream()
+ .map(group -> descriptors.stream()
                        .map(ModuleDescriptor::name)
                        .filter(group::contains)
                        .map(mn -> "\"" + mn + "\"")
- .collect(joining(","))
- ));
+ .collect(joining(",")))
+ .filter(group -> group.length() > 0)
+ .forEach(group -> out.format("{rank=same %s}%n", group));

            descriptors.stream()
                .filter(jdkGroup::contains)