1 files changed, 5 insertions, 2 deletions

diff --git a/enigma/src/main/java/cuchaz/enigma/source/SourceIndex.java b/enigma/src/main/java/cuchaz/enigma/source/SourceIndex.java
index a38c6f55..fec20e25 100644
--- a/enigma/src/main/java/cuchaz/enigma/source/SourceIndex.java
+++ b/enigma/src/main/java/cuchaz/enigma/source/SourceIndex.java
@@ -141,8 +141,11 @@ public class SourceIndex {
                         tokenToReference.replace(token, resolvedReference);
 
                         Collection<Token> tokens = referenceToTokens.remove(reference);
-                        referenceToTokens.computeIfAbsent(resolvedReference, key -> new ArrayList<>())
-                                        .addAll(tokens);
+
+                        if (tokens != null) {
+                                referenceToTokens.computeIfAbsent(resolvedReference, key -> new ArrayList<>())
+                                                .addAll(tokens);
+                        }
                 }
         }