diff --git a/src/main/java/io/optimism/config/ChainBigIntegerDecoder.java b/src/main/java/io/optimism/config/ChainBigIntegerDecoder.java
new file mode 100644
index 00000000..32c622f8
--- /dev/null
+++ b/src/main/java/io/optimism/config/ChainBigIntegerDecoder.java
@@ -0,0 +1,58 @@
+package io.optimism.config;
+
+import java.math.BigInteger;
+import org.apache.commons.lang3.StringUtils;
+import org.github.gestalt.config.decoder.DecoderContext;
+import org.github.gestalt.config.decoder.LeafDecoder;
+import org.github.gestalt.config.decoder.Priority;
+import org.github.gestalt.config.entity.ValidationError;
+import org.github.gestalt.config.node.ConfigNode;
+import org.github.gestalt.config.reflect.TypeCapture;
+import org.github.gestalt.config.tag.Tags;
+import org.github.gestalt.config.utils.GResultOf;
+
+/**
+ * Decode BigInteger field in Chain Config.
+ */
+public class ChainBigIntegerDecoder extends LeafDecoder<BigInteger> {
+
+    /**
+     * ChainBigIntegerDecoder constructor.
+     */
+    public ChainBigIntegerDecoder() {}
+
+    @Override
+    protected GResultOf<BigInteger> leafDecode(String path, ConfigNode node, DecoderContext decoderContext) {
+        GResultOf<BigInteger> results;
+        String value = node.getValue().orElse("");
+        if (!org.github.gestalt.config.utils.StringUtils.isReal(value)) {
+            results = GResultOf.errors(new ValidationError.DecodingNumberParsing(path, node, name()));
+        } else {
+            try {
+                BigInteger bigInteger = new BigInteger(value);
+                results = GResultOf.result(bigInteger);
+            } catch (NumberFormatException e) {
+                results = GResultOf.errors(new ValidationError.DecodingNumberParsing(path, node, name()));
+            }
+        }
+        return results;
+    }
+
+    @Override
+    public Priority priority() {
+        return Priority.HIGH;
+    }
+
+    @Override
+    public String name() {
+        return "BigInteger-Cust";
+    }
+
+    @Override
+    public boolean canDecode(String path, Tags tags, ConfigNode configNode, TypeCapture<?> type) {
+        if (StringUtils.isEmpty(path)) {
+            return false;
+        }
+        return path.startsWith("config.chainConfig") && BigInteger.class.isAssignableFrom(type.getRawType());
+    }
+}
diff --git a/src/main/java/io/optimism/config/Config.java b/src/main/java/io/optimism/config/Config.java
index 5c924f53..d98a5c32 100644
--- a/src/main/java/io/optimism/config/Config.java
+++ b/src/main/java/io/optimism/config/Config.java
@@ -103,12 +103,16 @@ public static Config create(Path configPath, CliConfig cliConfig, ChainConfig ch
             Map<String, String> cliProvider = cliConfig.toConfigMap();
 
             Gestalt gestalt;
+            final GestaltBuilder gestaltBuilder = new GestaltBuilder()
+                    .addDefaultDecoders()
+                    .addDecoder(new ChainBigIntegerDecoder())
+                    .addConfigLoader(environmentVarsLoader)
+                    .addConfigLoader(mapConfigLoader)
+                    .addConfigLoader(tomlLoader)
+                    .addConfigLoader(propertyLoader)
+                    .setTreatMissingValuesAsErrors(false);
             if (configPath != null) {
-                gestalt = new GestaltBuilder()
-                        .addConfigLoader(environmentVarsLoader)
-                        .addConfigLoader(mapConfigLoader)
-                        .addConfigLoader(tomlLoader)
-                        .addConfigLoader(propertyLoader)
+                gestalt = gestaltBuilder
                         .addSource(MapConfigSourceBuilder.builder()
                                 .setCustomConfig(defaultProvider)
                                 .build())
@@ -121,14 +125,9 @@ public static Config create(Path configPath, CliConfig cliConfig, ChainConfig ch
                         .addSource(MapConfigSourceBuilder.builder()
                                 .setCustomConfig(cliProvider)
                                 .build())
-                        .setTreatMissingValuesAsErrors(false)
                         .build();
             } else {
-                gestalt = new GestaltBuilder()
-                        .addConfigLoader(environmentVarsLoader)
-                        .addConfigLoader(mapConfigLoader)
-                        .addConfigLoader(tomlLoader)
-                        .addConfigLoader(propertyLoader)
+                gestalt = gestaltBuilder
                         .addSource(MapConfigSourceBuilder.builder()
                                 .setCustomConfig(defaultProvider)
                                 .build())
@@ -138,7 +137,6 @@ public static Config create(Path configPath, CliConfig cliConfig, ChainConfig ch
                         .addSource(MapConfigSourceBuilder.builder()
                                 .setCustomConfig(cliProvider)
                                 .build())
-                        .setTreatMissingValuesAsErrors(false)
                         .build();
             }
             gestalt.loadConfigs();
diff --git a/src/test/java/io/optimism/config/ConfigTest.java b/src/test/java/io/optimism/config/ConfigTest.java
index 4e2a9958..9e307fd4 100644
--- a/src/test/java/io/optimism/config/ConfigTest.java
+++ b/src/test/java/io/optimism/config/ConfigTest.java
@@ -105,7 +105,8 @@ void create() {
         assertEquals(
                 BigInteger.valueOf(188), config.chainConfig().systemConfig().l1FeeOverhead());
         assertEquals(
-                BigInteger.valueOf(684000), config.chainConfig().systemConfig().l1FeeScalar());
+                new BigInteger("452312848583266388373324160190187140051835877600158453279134670530344387928"),
+                config.chainConfig().systemConfig().l1FeeScalar());
         assertEquals(
                 "0xff00000000000000000000000000000011155420",
                 config.chainConfig().batchInbox());
diff --git a/src/test/resources/test.toml b/src/test/resources/test.toml
index 2be452f7..e46b06ba 100644
--- a/src/test/resources/test.toml
+++ b/src/test/resources/test.toml
@@ -2,4 +2,7 @@
 l2RpcUrl = "https://example2.com"
 
 [config.chainConfig]
-seqWindowSize = 111_111_111
\ No newline at end of file
+seqWindowSize = 111_111_111
+
+[config.chainConfig.systemConfig]
+l1FeeScalar = 452312848583266388373324160190187140051835877600158453279134670530344387928
\ No newline at end of file