diff --git a/src/main/java/PasswordGenerator.java b/src/main/java/PasswordGenerator.java
index 178ef78..5afed60 100644
--- a/src/main/java/PasswordGenerator.java
+++ b/src/main/java/PasswordGenerator.java
@@ -38,13 +38,13 @@ public class PasswordGenerator {
 
             if (isRequireEveryConfiguredCharacterType()) {
                 if (generatorPosition == 0 && isUseLowercase()) {
-                    customCharacterPool += lowercaseCharacters;
+                    customCharacterPool = lowercaseCharacters;
                 } else if (generatorPosition == 1 && isUseUppercase()) {
-                    customCharacterPool += uppercaseCharacters;
+                    customCharacterPool = uppercaseCharacters;
                 } else if (generatorPosition == 2 && isUseDigits()) {
-                    customCharacterPool += digits;
+                    customCharacterPool = digits;
                 } else if (generatorPosition == 3 && isUseSpecialCharacters()) {
-                    customCharacterPool += specialCharacters;
+                    customCharacterPool = specialCharacters;
                 } else {
                     customCharacterPool = characterPool;
                 }