diff --git a/crates/build/README.md b/crates/build/README.md
index bcf1e65cb..b558083e8 100644
--- a/crates/build/README.md
+++ b/crates/build/README.md
@@ -12,6 +12,7 @@ use contract_build::{
     BuildArtifacts,
     BuildMode,
     Features,
+    MetadataSpec,
     Network,
     OutputType,
     UnstableFlags,
@@ -34,6 +35,7 @@ let args = contract_build::ExecuteArgs {
     output_type: OutputType::Json,
     skip_clippy_and_linting: false,
     image: ImageVariant::Default,
+    metadata_spec: MetadataSpec::Ink,
 };
 
 contract_build::execute(args);
diff --git a/crates/build/src/args.rs b/crates/build/src/args.rs
index fe68b8573..324620279 100644
--- a/crates/build/src/args.rs
+++ b/crates/build/src/args.rs
@@ -285,9 +285,11 @@ impl Features {
     serde::Serialize,
     serde::Deserialize,
 )]
+#[serde(rename_all = "lowercase")]
 pub enum MetadataSpec {
     /// ink!
     #[clap(name = "ink")]
+    #[serde(rename = "ink!")]
     #[default]
     Ink,
     /// Solidity
diff --git a/crates/build/src/lib.rs b/crates/build/src/lib.rs
index aea6be142..c431d3d74 100644
--- a/crates/build/src/lib.rs
+++ b/crates/build/src/lib.rs
@@ -1068,6 +1068,7 @@ mod unit_tests {
         let raw_result = r#"{
   "dest_binary": "/path/to/contract.polkavm",
   "metadata_result": {
+    "spec": "ink!",
     "dest_metadata": "/path/to/contract.json",
     "dest_bundle": "/path/to/contract.contract"
   },
@@ -1085,6 +1086,7 @@ mod unit_tests {
         let build_result = BuildResult {
             dest_binary: Some(PathBuf::from("/path/to/contract.polkavm")),
             metadata_result: Some(MetadataArtifacts {
+                spec: MetadataSpec::Ink,
                 dest_metadata: PathBuf::from("/path/to/contract.json"),
                 dest_bundle: PathBuf::from("/path/to/contract.contract"),
             }),