1 files changed, 1 insertions, 2 deletions

diff --git a/src/main/java/cuchaz/enigma/analysis/JarIndex.java b/src/main/java/cuchaz/enigma/analysis/JarIndex.java
index 87e6e88..8172dea 100644
--- a/src/main/java/cuchaz/enigma/analysis/JarIndex.java
+++ b/src/main/java/cuchaz/enigma/analysis/JarIndex.java
@@ -148,8 +148,7 @@ public class JarIndex {
 
         public void indexInnerClass(ClassEntry innerEntry, ClassEntry outerEntry) {
                 this.innerClassesByOuter.put(outerEntry, innerEntry);
-                boolean innerWasAdded = this.outerClassesByInner.put(innerEntry, outerEntry) == null;
-                assert (innerWasAdded);
+                this.outerClassesByInner.putIfAbsent(innerEntry, outerEntry);
         }
 
         private MethodEntry findBridgedMethod(MethodDefEntry method) {