diff --git a/src/main/java/codegen/flowgraph/FlowGraphGenerator.java b/src/main/java/codegen/flowgraph/FlowGraphGenerator.java
index 7784417..b270a60 100644
--- a/src/main/java/codegen/flowgraph/FlowGraphGenerator.java
+++ b/src/main/java/codegen/flowgraph/FlowGraphGenerator.java
@@ -407,6 +407,6 @@ public final class FlowGraphGenerator {
     // Getters, Setters
 
     public Map<String, Integer> getVarMap() {
-        return this.varMap;
+        return Collections.unmodifiableMap(this.varMap);
     }
 }