diff --git a/src/main/java/uk/org/okapibarcode/backend/Pdf417.java b/src/main/java/uk/org/okapibarcode/backend/Pdf417.java
index 996c13c8..35bb352b 100644
--- a/src/main/java/uk/org/okapibarcode/backend/Pdf417.java
+++ b/src/main/java/uk/org/okapibarcode/backend/Pdf417.java
@@ -1810,7 +1810,7 @@ private int addMacroCodewords() {
             codeWords[codeWordCount++] = 923;
             codeWords[codeWordCount++] = 000;
             EciMode eci = EciMode.chooseFor(structuredAppendFileName, 3, 26);
-            int[] data2 = toBytes(structuredAppendFileName, eci.charset);
+            int[] data2 = toBytes(structuredAppendFileName, eci.getCharset());
             processEci(eci.mode);
             processText(data2, 0, data2.length, true);
         }
diff --git a/src/main/java/uk/org/okapibarcode/backend/Symbol.java b/src/main/java/uk/org/okapibarcode/backend/Symbol.java
index 231b74a0..35c1b218 100644
--- a/src/main/java/uk/org/okapibarcode/backend/Symbol.java
+++ b/src/main/java/uk/org/okapibarcode/backend/Symbol.java
@@ -31,6 +31,7 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
+import java.util.Optional;
 
 import uk.org.okapibarcode.graphics.Circle;
 import uk.org.okapibarcode.graphics.Hexagon;
@@ -414,7 +415,7 @@ public void setEciMode(int eciMode) {
         if (!supportsEci()) {
             throw new IllegalArgumentException("This symbology type does not support ECI");
         }
-        boolean valid = EciMode.ECIS.stream().anyMatch(eci -> eci.mode == eciMode);
+        boolean valid = Optional.ofNullable(EciMode.ECIS.get(eciMode)).filter(EciMode::isSupported).isPresent();
         if (!valid) {
             throw new IllegalArgumentException("Unsupported ECI mode: " + eciMode);
         }
@@ -678,7 +679,7 @@ protected void eciProcess() {
         EciMode eci;
         if (eciMode != -1) {
             // user chose the ECI mode explicitly
-            eci = EciMode.ECIS.stream().filter(e -> e.mode == eciMode).findFirst().orElse(EciMode.NONE);
+            eci = Optional.ofNullable(EciMode.ECIS.get(eciMode)).filter(EciMode::isSupported).orElse(EciMode.NONE);
         } else {
             // detect the ECI mode automatically
             eci = EciMode.chooseFor(content);
@@ -689,7 +690,7 @@ protected void eciProcess() {
         }
 
         eciMode = eci.mode;
-        inputData = toBytes(content, eci.charset);
+        inputData = toBytes(content, eci.getCharset());
 
         if (inputData == null) {
             // user chose the ECI mode explicitly and it can't encode the provided data
@@ -697,7 +698,7 @@ protected void eciProcess() {
         }
 
         infoLine("ECI Mode: " + eci.mode);
-        infoLine("ECI Charset: " + eci.charset.name());
+        infoLine("ECI Charset: " + eci.charsetName);
     }
 
     protected static int[] toBytes(String s, Charset charset, int... suffix) {
diff --git a/src/main/java/uk/org/okapibarcode/util/EciMode.java b/src/main/java/uk/org/okapibarcode/util/EciMode.java
index 4a63ca00..192903b9 100644
--- a/src/main/java/uk/org/okapibarcode/util/EciMode.java
+++ b/src/main/java/uk/org/okapibarcode/util/EciMode.java
@@ -19,10 +19,11 @@
 import static uk.org.okapibarcode.util.Arrays.contains;
 
 import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.nio.charset.UnsupportedCharsetException;
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.Map;
 
 /**
  * Represents an ECI (Extended Channel Interpretation) mode. Each ECI mode corresponds to a particular
@@ -36,69 +37,92 @@ public final class EciMode {
 
     /** Represents "no ECI" or "missing ECI". */
     public static final EciMode NONE = new EciMode(-1, null);
+    private static final EciMode ISO_8859_1 = new EciMode(3, "ISO-8859-1");
+    private static final EciMode UTF_8 = new EciMode(26, "UTF-8");
+    private static final EciMode US_ASCII = new EciMode(27, "US-ASCII");
 
     /** The available ECI modes, in priority order. */
-    public static List< EciMode > ECIS = Collections.unmodifiableList(Arrays.asList(
-        EciMode.of(3, "ISO-8859-1"),
-        EciMode.of(4, "ISO-8859-2"),
-        EciMode.of(5, "ISO-8859-3"),
-        EciMode.of(6, "ISO-8859-4"),
-        EciMode.of(7, "ISO-8859-5"),
-        EciMode.of(8, "ISO-8859-6"),
-        EciMode.of(9, "ISO-8859-7"),
-        EciMode.of(10, "ISO-8859-8"),
-        EciMode.of(11, "ISO-8859-9"),
-        EciMode.of(12, "ISO-8859-10"), // not usually supported by Java
-        EciMode.of(13, "ISO-8859-11"),
-        EciMode.of(15, "ISO-8859-13"),
-        EciMode.of(16, "ISO-8859-14"), // not usually supported by Java
-        EciMode.of(17, "ISO-8859-15"),
-        EciMode.of(18, "ISO-8859-16"), // not usually supported by older Java versions
-        EciMode.of(21, "windows-1250"),
-        EciMode.of(22, "windows-1251"),
-        EciMode.of(23, "windows-1252"),
-        EciMode.of(24, "windows-1256"),
-        EciMode.of(20, "Shift_JIS"),
-        EciMode.of(26, "UTF-8"),
+    public static final LinkedHashMap<Integer, EciMode> ECIS = new LinkedHashMap<>();
+
+    static {
+        ECIS.put(3, ISO_8859_1);
+        ECIS.put(4, new EciMode(4, "ISO-8859-2"));
+        ECIS.put(5, new EciMode(5, "ISO-8859-3"));
+        ECIS.put(6, new EciMode(6, "ISO-8859-4"));
+        ECIS.put(7, new EciMode(7, "ISO-8859-5"));
+        ECIS.put(8, new EciMode(8, "ISO-8859-6"));
+        ECIS.put(9, new EciMode(9, "ISO-8859-7"));
+        ECIS.put(10, new EciMode(10, "ISO-8859-8"));
+        ECIS.put(11, new EciMode(11, "ISO-8859-9"));
+        ECIS.put(12, new EciMode(12, "ISO-8859-10")); // not usually supported by Jav);a
+        ECIS.put(13, new EciMode(13, "ISO-8859-11"));
+        ECIS.put(15, new EciMode(15, "ISO-8859-13"));
+        ECIS.put(16, new EciMode(16, "ISO-8859-14")); // not usually supported by Jav);a
+        ECIS.put(17, new EciMode(17, "ISO-8859-15"));
+        ECIS.put(18, new EciMode(18, "ISO-8859-16")); // not usually supported by older Java version);s
+        ECIS.put(21, new EciMode(21, "windows-1250"));
+        ECIS.put(22, new EciMode(22, "windows-1251"));
+        ECIS.put(23, new EciMode(23, "windows-1252"));
+        ECIS.put(24, new EciMode(24, "windows-1256"));
+        ECIS.put(20, new EciMode(20, "Shift_JIS"));
+        ECIS.put(26, UTF_8);
         // UTF-8 is the final fallback when automatically detecting the ECI, since it can encode anything.
         // The ECI modes below are available to be requested explicitly, but are never used automatically.
-        EciMode.of(0, "IBM437"),
-        EciMode.of(1, "ISO-8859-1"),
-        EciMode.of(2, "IBM437"),
-        EciMode.of(25, "UTF-16BE"),
-        EciMode.of(27, "US-ASCII"),
-        EciMode.of(28, "Big5"),
-        EciMode.of(29, "GB2312"),
-        EciMode.of(30, "EUC-KR"),
-        EciMode.of(31, "GBK"),
-        EciMode.of(32, "GB18030"),
-        EciMode.of(33, "UTF-16LE"),
-        EciMode.of(34, "UTF-32BE"),
-        EciMode.of(35, "UTF-32LE")));
+        ECIS.put(0, new EciMode(0, "IBM437"));
+        ECIS.put(1, new EciMode(1, "ISO-8859-1"));
+        ECIS.put(2, new EciMode(2, "IBM437"));
+        ECIS.put(25, new EciMode(25, "UTF-16BE"));
+        ECIS.put(27, US_ASCII);
+        ECIS.put(28, new EciMode(28, "Big5"));
+        ECIS.put(29, new EciMode(29, "GB2312"));
+        ECIS.put(30, new EciMode(30, "EUC-KR"));
+        ECIS.put(31, new EciMode(31, "GBK"));
+        ECIS.put(32, new EciMode(32, "GB18030"));
+        ECIS.put(33, new EciMode(33, "UTF-16LE"));
+        ECIS.put(34, new EciMode(34, "UTF-32BE"));
+        ECIS.put(35, new EciMode(35, "UTF-32LE"));
+    }
 
     public final int mode;
-    public final Charset charset;
+    public final String charsetName;
+
+    private static final HashMap<EciMode, Charset> ECI_CHARSETS = new HashMap<>(ECIS.size());
+
+    static {
+        ECI_CHARSETS.put(ISO_8859_1, StandardCharsets.ISO_8859_1);
+        ECI_CHARSETS.put(UTF_8, StandardCharsets.UTF_8);
+        ECI_CHARSETS.put(US_ASCII, StandardCharsets.US_ASCII);
+    }
 
-    private EciMode(int mode, Charset charset) {
+    private EciMode(int mode, String charsetName) {
         this.mode = mode;
-        this.charset = charset;
+        this.charsetName = charsetName;
+    }
+
+    public Charset getCharset() {
+        return ECI_CHARSETS.computeIfAbsent(this, this::loadCharset);
+    }
+
+    public boolean isSupported() {
+        return getCharset() != null;
     }
 
-    private static EciMode of(int mode, String charsetName) {
+    private Charset loadCharset(EciMode eciMode) {
         try {
-            return new EciMode(mode, Charset.forName(charsetName));
+            return Charset.forName(eciMode.charsetName);
         } catch (UnsupportedCharsetException e) {
-            return NONE;
+            return null;
         }
     }
 
     public static EciMode chooseFor(String data, int... filter) {
-        for (EciMode eci : ECIS) {
-            if (eci.charset != null
-                && eci.charset.canEncode()
-                && eci.charset.newEncoder().canEncode(data)
-                && (filter.length == 0 || contains(filter, eci.mode))) {
-                return eci;
+        for (Map.Entry<Integer, EciMode> eci : ECIS.entrySet()) {
+            Charset charset = eci.getValue().getCharset();
+            if (charset != null
+                    && charset.canEncode()
+                    && charset.newEncoder().canEncode(data)
+                    && (filter.length == 0 || contains(filter, eci.getKey()))) {
+                return eci.getValue();
             }
         }
         return NONE;
@@ -116,6 +140,6 @@ public int hashCode() {
 
     @Override
     public String toString() {
-        return "EciMode[mode=" + mode + ", charset=" + charset + "]";
+        return "EciMode[mode=" + mode + ", charset=" + charsetName + "]";
     }
 }
diff --git a/src/test/resources/uk/org/okapibarcode/backend/pdf417/normal-eci-13.properties b/src/test/resources/uk/org/okapibarcode/backend/pdf417/normal-eci-13.properties
index 03104778..b59f411a 100644
--- a/src/test/resources/uk/org/okapibarcode/backend/pdf417/normal-eci-13.properties
+++ b/src/test/resources/uk/org/okapibarcode/backend/pdf417/normal-eci-13.properties
@@ -6,7 +6,7 @@ content=te\u0E24t
 LOG
 
 ECI Mode: 13
-ECI Charset: x-iso-8859-11
+ECI Charset: ISO-8859-11
 Codewords: 8 927 13 829 149 901 196 116
 Length Descriptor Codewords: 1
 Data Codewords: 7