diff --git a/agent/src/artifact/upload.rs b/agent/src/artifact/upload.rs
index 927ba8647f..e968e42626 100644
--- a/agent/src/artifact/upload.rs
+++ b/agent/src/artifact/upload.rs
@@ -419,11 +419,9 @@ impl Uploader {
     ) -> Result<()> {
         let artifact = artifact.display().to_string();
         let mut args = vec!["artifact", "upload"];
-        let ct_arg = content_type
-            .map(|ct| "--content_type=".to_owned() + ct)
-            .unwrap_or_default();
-        if !ct_arg.is_empty() {
-            args.push(ct_arg.as_str());
+        if let Some(content_type) = content_type {
+            args.push("--content-type");
+            args.push(content_type);
         }
         args.push(artifact.as_str());
         execute_command(dry, cwd, "buildkite-agent", &args)
diff --git a/agent/tests/artifact/upload.rs b/agent/tests/artifact/upload.rs
index 8a892c84e9..6d210c5ca3 100644
--- a/agent/tests/artifact/upload.rs
+++ b/agent/tests/artifact/upload.rs
@@ -19,7 +19,7 @@ fn test_logs_uploaded_to_buildkite() -> Result<()> {
     ]);
     cmd.assert()
         .success()
-        .stdout(predicates::ord::eq("buildkite-agent artifact upload --content_type=text/plain;encoding=utf-8 src\\test\\shell\\bazel\\resource_compiler_toolchain_test\\test.log\n"));
+        .stdout(predicates::ord::eq("buildkite-agent artifact upload --content-type text/plain;encoding=utf-8 src\\test\\shell\\bazel\\resource_compiler_toolchain_test\\test.log\n"));
 
     Ok(())
 }
@@ -37,7 +37,7 @@ fn test_logs_uploaded_to_buildkite() -> Result<()> {
     ]);
     cmd.assert()
         .success()
-        .stdout(predicates::ord::eq("buildkite-agent artifact upload --content_type=text/plain;encoding=utf-8 src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log\n"));
+        .stdout(predicates::ord::eq("buildkite-agent artifact upload --content-type text/plain;encoding=utf-8 src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log\n"));
 
     Ok(())
 }
@@ -139,7 +139,7 @@ fn test_logs_deduplicated() -> Result<()> {
     ]);
     cmd.assert()
         .success()
-        .stdout(predicates::str::contains("buildkite-agent artifact upload --content_type=text/plain;encoding=utf-8 src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log").count(1));
+        .stdout(predicates::str::contains("buildkite-agent artifact upload --content-type text/plain;encoding=utf-8 src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log").count(1));
 
     Ok(())
 }
@@ -178,7 +178,7 @@ fn test_running_json_file() -> Result<()> {
 
         cmd.assert()
         .success()
-        .stdout(predicates::str::contains("buildkite-agent artifact upload --content_type=text/plain;encoding=utf-8 src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log"));
+        .stdout(predicates::str::contains("buildkite-agent artifact upload --content-type text/plain;encoding=utf-8 src/test/shell/bazel/starlark_repository_test/shard_4_of_6/test_attempts/attempt_1.log"));
         Ok(())
     })
 }