diff --git a/grammar.js b/grammar.js
index 1907a3a3..3cf16438 100644
--- a/grammar.js
+++ b/grammar.js
@@ -488,11 +488,12 @@ module.exports = grammar({
       field('bounds', $.trait_bounds),
     ),
 
-    impl_item: $ => seq(
+    impl_item: $ => prec(1, seq(
       optional('unsafe'),
       'impl',
       field('type_parameters', optional($.type_parameters)),
       optional(seq(
+        optional('const'),
         optional('!'),
         field('trait', choice(
           $._type_identifier,
@@ -504,7 +505,7 @@ module.exports = grammar({
       field('type', $._type),
       optional($.where_clause),
       choice(field('body', $.declaration_list), ';'),
-    ),
+    )),
 
     trait_item: $ => seq(
       optional($.visibility_modifier),
diff --git a/test/corpus/declarations.txt b/test/corpus/declarations.txt
index 77195e86..044ecdf3 100644
--- a/test/corpus/declarations.txt
+++ b/test/corpus/declarations.txt
@@ -1667,6 +1667,21 @@ unsafe impl Foo {
     (type_identifier)
     (declaration_list)))
 
+================================================================================
+Const impls
+================================================================================
+
+impl const Foo for Bar {
+}
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (impl_item
+    (type_identifier)
+    (type_identifier)
+    (declaration_list)))
+
 ================================================================================
 Disable automatically derived trait impls
 ================================================================================