diff --git a/src/parse/args.rs b/src/parse/args.rs
index a10cc4e..da5b0c7 100644
--- a/src/parse/args.rs
+++ b/src/parse/args.rs
@@ -231,8 +231,24 @@ impl<'a> Parser<'a> {
                         }
                     }
                     Value::Map(v) => {
-                        for (name, arg) in v.entries() {
-                            let name = name.to_css_string(val.span)?.to_string();
+                        // NOTE: we clone the map here because it is used
+                        // later for error reporting. perhaps there is
+                        // some way around this?
+                        for (name, arg) in v.clone().entries() {
+                            let name = match name {
+                                Value::String(s, ..) => s,
+                                _ => {
+                                    return Err((
+                                        format!(
+                                            "{} is not a string in {}.",
+                                            name.inspect(val.span)?,
+                                            Value::Map(v).inspect(val.span)?
+                                        ),
+                                        val.span,
+                                    )
+                                        .into())
+                                }
+                            };
                             args.insert(CallArg::Named(name.into()), Ok(arg.span(val.span)));
                         }
                     }
diff --git a/tests/splat.rs b/tests/splat.rs
index e36e664..c5b3166 100644
--- a/tests/splat.rs
+++ b/tests/splat.rs
@@ -33,6 +33,13 @@ test!(
     }",
     "a {\n  color: 1;\n}\n"
 );
+test!(
+    splat_map_quoted_string_as_key,
+    "a {
+        color: red((\"color\": red)...);
+    }",
+    "a {\n  color: 255;\n}\n"
+);
 error!(
     splat_missing_last_period,
     "@function foo($a) {
@@ -53,3 +60,17 @@ error!(
     }",
     "Error: expected \")\"."
 );
+error!(
+    splat_map_with_non_string_key_map,
+    "a {
+        color: red(((a: b): red)...);
+    }",
+    "Error: (a: b) is not a string in ((a: b): red)."
+);
+error!(
+    splat_map_with_non_string_key_number,
+    "a {
+        color: red((1: red)...);
+    }",
+    "Error: 1 is not a string in (1: red)."
+);