diff --git a/src/main/java/hudson/maven/AbstractMavenBuilder.java b/src/main/java/hudson/maven/AbstractMavenBuilder.java
index ebf7a55b..0a9d01c0 100644
--- a/src/main/java/hudson/maven/AbstractMavenBuilder.java
+++ b/src/main/java/hudson/maven/AbstractMavenBuilder.java
@@ -98,7 +98,13 @@ protected AbstractMavenBuilder(BuildListener listener, Collection<MavenModule> m
     void end(Launcher launcher) throws IOException, InterruptedException {
         for (Map.Entry<ModuleName,ProxyImpl2> e : sourceProxies.entrySet()) {
             ProxyImpl2 p = e.getValue();
-            for (MavenReporter r : reporters.get(e.getKey())) {
+            ModuleName module = e.getKey();
+            List<MavenReporter> moduleReporters = reporters.get(module);
+            if (moduleReporters == null) {
+                // Safety: Key set of reporter and source list has become inconsistent.
+                continue;
+            }
+            for (MavenReporter r : moduleReporters) {
                 // we'd love to do this when the module build ends, but doing so requires
                 // we know how many task segments are in the current build.
                 r.end(p.owner(),launcher,listener);