diff --git a/src/bin/commands/rustc.rs b/src/bin/commands/rustc.rs
index 268b835a630..b53e5a8abd1 100644
--- a/src/bin/commands/rustc.rs
+++ b/src/bin/commands/rustc.rs
@@ -62,7 +62,12 @@ pub fn exec(config: &mut Config, args: &ArgMatches) -> CliResult {
         }
     };
     let mut compile_opts = args.compile_options_for_single_package(config, mode)?;
-    compile_opts.target_rustc_args = Some(values(args, "args"));
+    let target_args = values(args, "args");
+    compile_opts.target_rustc_args = if target_args.is_empty() {
+        None
+    } else {
+        Some(target_args)
+    };
     ops::compile(&ws, &compile_opts)?;
     Ok(())
 }
diff --git a/src/bin/commands/rustdoc.rs b/src/bin/commands/rustdoc.rs
index f3744cebf16..1712b855992 100644
--- a/src/bin/commands/rustdoc.rs
+++ b/src/bin/commands/rustdoc.rs
@@ -49,7 +49,12 @@ pub fn exec(config: &mut Config, args: &ArgMatches) -> CliResult {
     let ws = args.workspace(config)?;
     let mut compile_opts =
         args.compile_options_for_single_package(config, CompileMode::Doc { deps: false })?;
-    compile_opts.target_rustdoc_args = Some(values(args, "args"));
+    let target_args = values(args, "args");
+    compile_opts.target_rustdoc_args = if target_args.is_empty() {
+        None
+    } else {
+        Some(target_args)
+    };
     let doc_opts = DocOptions {
         open_result: args.is_present("open"),
         compile_opts,