diff --git a/backend/src/main/java/com/crypto/Caesar.java b/backend/src/main/java/com/crypto/Caesar.java
index 3a2be3a..3fead4a 100644
--- a/backend/src/main/java/com/crypto/Caesar.java
+++ b/backend/src/main/java/com/crypto/Caesar.java
@@ -6,7 +6,8 @@ public class Caesar {
         char encoded[] = plaintext.toCharArray();
 
         for(int i = 0; i < plaintext.length(); i++){
-            encoded[i] = alphabet.charAt(alphabet.indexOf(encoded[i]) + key % 26);
+            if (alphabet.indexOf(encoded[i]) == -1) continue;
+            encoded[i] = alphabet.charAt((alphabet.indexOf(encoded[i]) + key) % 26);
         }
         return String.valueOf(encoded);
     }
@@ -21,6 +22,10 @@ public class Caesar {
         for(int key = 0; key < alphabet.length(); key++){
 
             for(int i = 0; i < ciphertext.length(); i++){
+                if (alphabet.indexOf(encoded[i]) == -1) {
+                    decoded[i] = encoded[i];
+                    continue;
+                }
                 char current = encoded[i];
                 int pos = alphabet.indexOf(current);
                 if(pos != -1) {