diff --git a/gradle.properties b/gradle.properties
index 726293bd..cbb322b2 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -3,7 +3,7 @@ org.gradle.daemon=false
 
 mod_id=sophisticatedbackpacks
 mod_group_id=sophisticatedbackpacks
-mod_version=3.20.2
+mod_version=3.20.3
 sonar_project_key=sophisticatedbackpacks:SophisticatedBackpacks
 github_package_url=https://maven.pkg.github.com/P3pp3rF1y/SophisticatedBackpacks
 
diff --git a/src/main/java/net/p3pp3rf1y/sophisticatedbackpacks/Config.java b/src/main/java/net/p3pp3rf1y/sophisticatedbackpacks/Config.java
index bd280980..79f19100 100644
--- a/src/main/java/net/p3pp3rf1y/sophisticatedbackpacks/Config.java
+++ b/src/main/java/net/p3pp3rf1y/sophisticatedbackpacks/Config.java
@@ -36,6 +36,7 @@
 public class Config {
 
 	private static final String REGISTRY_NAME_MATCHER = "([a-z0-9_.-]+:[a-z0-9_/.-]+)";
+	private static final String MAX_UPGRADES_MATCHER = "([a-z0-9_/.-]+\\|\\d+)";
 
 	private Config() {
 	}
@@ -445,13 +446,14 @@ private void loadDisallowedSet() {
 		}
 
 		public static class MaxUgradesPerStorageConfig implements IUpgradeCountLimitConfig {
-			private final ForgeConfigSpec.ConfigValue<List<String>> maxUpgradesPerStorageList;
+			private final ForgeConfigSpec.ConfigValue<List<? extends String>> maxUpgradesPerStorageList;
 
 			@Nullable
 			private Map<String, Integer> maxUpgradesPerStorage = null;
 
 			protected MaxUgradesPerStorageConfig(ForgeConfigSpec.Builder builder, Map<String, Integer> defaultUpgradesPerStorage) {
-				maxUpgradesPerStorageList = builder.comment("Maximum number of upgrades of type per backpack in format of \"UpgradeRegistryName[or UpgradeGroup]|MaxNumber\"").define("maxUpgradesPerStorage", convertToList(defaultUpgradesPerStorage));
+				maxUpgradesPerStorageList = builder.comment("Maximum number of upgrades of type per backpack in format of \"UpgradeRegistryName[or UpgradeGroup]|MaxNumber\"")
+						.defineList("maxUpgradesPerStorage", convertToList(defaultUpgradesPerStorage), mapping -> ((String) mapping).matches(MAX_UPGRADES_MATCHER));
 			}
 
 			private List<String> convertToList(Map<String, Integer> defaultUpgradesPerStorage) {