diff --git a/crates/uv-pypi-types/src/dependency_groups.rs b/crates/uv-pypi-types/src/dependency_groups.rs
index 4365c2cf2e..e933386258 100644
--- a/crates/uv-pypi-types/src/dependency_groups.rs
+++ b/crates/uv-pypi-types/src/dependency_groups.rs
@@ -129,12 +129,13 @@ impl<'de> Deserialize<'de> for DependencyGroupSpecifier {
                     return Err(serde::de::Error::custom("missing field `include-group`"));
                 }
 
-                if let Some(include_group) = map_data
-                    .get("include-group")
-                    .map(String::as_str)
-                    .map(GroupName::from_str)
-                    .transpose()
-                    .map_err(serde::de::Error::custom)?
+                if map_data.len() == 1
+                    && let Some(include_group) = map_data
+                        .get("include-group")
+                        .map(String::as_str)
+                        .map(GroupName::from_str)
+                        .transpose()
+                        .map_err(serde::de::Error::custom)?
                 {
                     Ok(DependencyGroupSpecifier::IncludeGroup { include_group })
                 } else {
diff --git a/crates/uv-workspace/src/workspace.rs b/crates/uv-workspace/src/workspace.rs
index f9a0cf6d64..7957fe825a 100644
--- a/crates/uv-workspace/src/workspace.rs
+++ b/crates/uv-workspace/src/workspace.rs
@@ -2178,6 +2178,7 @@ impl VirtualProject {
 #[cfg(test)]
 #[cfg(unix)] // Avoid path escaping for the unit tests
 mod tests {
+    use std::collections::BTreeMap;
     use std::env;
     use std::path::Path;
     use std::str::FromStr;
@@ -3244,6 +3245,7 @@ mod tests {
 [dependency-groups]
 foo = ["a", {include-group = "bar"}]
 bar = ["b"]
+future = [{include-group = "bar", unknown = "value"}]
 "#;
 
         let result = PyProjectToml::from_string(toml.to_string(), "pyproject.toml")
@@ -3272,6 +3274,17 @@ bar = ["b"]
             bar,
             &[DependencyGroupSpecifier::Requirement("b".to_string())]
         );
+
+        let future = groups
+            .get(&GroupName::from_str("future").unwrap())
+            .expect("Group `future` should be present");
+        assert_eq!(
+            future,
+            &[DependencyGroupSpecifier::Object(BTreeMap::from([
+                ("include-group".to_string(), "bar".to_string()),
+                ("unknown".to_string(), "value".to_string()),
+            ]))]
+        );
     }
 
     #[tokio::test]
diff --git a/crates/uv/tests/lock/lock.rs b/crates/uv/tests/lock/lock.rs
index 3cbbf92df9..025133a473 100644
--- a/crates/uv/tests/lock/lock.rs
+++ b/crates/uv/tests/lock/lock.rs
@@ -26231,6 +26231,38 @@ fn lock_group_invalid_entry_table() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn lock_group_include_with_extra_key() -> Result<()> {
+    let context = uv_test::test_context!("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+
+        [dependency-groups]
+        foo = [{include-group = "bar", unknown = "value"}]
+        bar = []
+        "#,
+    )?;
+
+    uv_snapshot!(context.filters(), context.lock(), @r#"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Project `project` has malformed dependency groups
+      Caused by: Group `foo` contains an unknown dependency object specifier: {"include-group": "bar", "unknown": "value"}
+    "#);
+
+    Ok(())
+}
+
 #[test]
 fn lock_group_invalid_entry_type() -> Result<()> {
     let context = uv_test::test_context!("3.12");