diff --git a/plugins/maven/src/main/java/org/jetbrains/idea/maven/importing/MavenModuleNameMapper.java b/plugins/maven/src/main/java/org/jetbrains/idea/maven/importing/MavenModuleNameMapper.java
index c125e65db08e..c9736b2926d0 100644
--- a/plugins/maven/src/main/java/org/jetbrains/idea/maven/importing/MavenModuleNameMapper.java
+++ b/plugins/maven/src/main/java/org/jetbrains/idea/maven/importing/MavenModuleNameMapper.java
@@ -102,7 +102,10 @@ public class MavenModuleNameMapper {
       mavenProjectToModuleName.put(each.project, each.getResultName());
     }
 
-    assert new HashSet<String>(mavenProjectToModuleName.values()).size() == mavenProjectToModuleName.size();
+    assert new HashSet<String>(mavenProjectToModuleName.values()).size() == mavenProjectToModuleName.size() : mavenProjectToModuleName
+                                                                                                                .values() +
+                                                                                                              "\n||\n" +
+                                                                                                              mavenProjectToModuleName;
   }
 
   public static class NameItem implements Comparable<NameItem> {