diff --git a/src/atrule/mod.rs b/src/atrule/mod.rs
index de84405..ef22bea 100644
--- a/src/atrule/mod.rs
+++ b/src/atrule/mod.rs
@@ -70,7 +70,7 @@ impl AtRule {
                     super_selector,
                 )?;
 
-                return Err((message.to_css_string(span)?, span.merge(kind_span)).into());
+                return Err((message.inspect(span)?, span.merge(kind_span)).into());
             }
             AtRuleKind::Warn => {
                 let Spanned {
diff --git a/tests/at-error.rs b/tests/at-error.rs
index 2d9f873..e9c6865 100644
--- a/tests/at-error.rs
+++ b/tests/at-error.rs
@@ -13,3 +13,4 @@ error!(
 );
 error!(error_unquoted_string, "a {\n  @error hi;\n}\n", "Error: hi");
 error!(error_arithmetic, "a {\n  @error 1 + 1;\n}\n", "Error: 2");
+error!(error_is_inspected, "a {\n  @error null;\n}\n", "Error: null");