diff --git a/fuzz/src/main/java/edu/berkeley/cs/jqf/fuzz/ei/ir/TypedInputStream.java b/fuzz/src/main/java/edu/berkeley/cs/jqf/fuzz/ei/ir/TypedInputStream.java
index fdb613d9f..58db3539d 100644
--- a/fuzz/src/main/java/edu/berkeley/cs/jqf/fuzz/ei/ir/TypedInputStream.java
+++ b/fuzz/src/main/java/edu/berkeley/cs/jqf/fuzz/ei/ir/TypedInputStream.java
@@ -87,7 +87,7 @@ public String readString(List<String> dictionary) throws IOException {
         TypedGeneratedValue ret = readValue(TypedGeneratedValue.Type.String);
         bytesRead+=4; //Historically JQF has counted strings as 4 bytes (an int into a dictionary)
         positionInInput++;
-        return dictionary.get(((TypedGeneratedValue.StringValue) ret).keyNotBoundedBySize % dictionary.size());
+        return dictionary.get(Math.abs(((TypedGeneratedValue.StringValue) ret).keyNotBoundedBySize % dictionary.size()));
     }
 
     public char readChar() throws IOException {