diff --git a/grammar.js b/grammar.js
index 7395f02..7283a5e 100644
--- a/grammar.js
+++ b/grammar.js
@@ -32,8 +32,16 @@ const attrAlias = mkAlias(($) => $.attribute);
 // mkAttrCont :: ($ -> Rule) -> ($ -> Rule) -> $ -> Rule
 const mkAttrCont = (onValue) => (onKey) => ($) =>
   seq(onKey($), $._colon, onValue($));
-const mkBaseAttr = (onKey) =>
-  mkAttrCont(($) => $.attr_value)(attrKeyAlias(onKey));
+const mkAttr = (onKey) => mkAttrCont(($) => $.attr_value)(attrKeyAlias(onKey));
+const mkListAttr = (onKey) =>
+  mkAttrCont(
+    either(
+      ($) => $.attr_value_list,
+      ($) => $.attr_value
+    )
+  )(attrKeyAlias(onKey));
+
+const either = (onLeft, onRight) => ($) => choice(onLeft($), onRight($));
 
 module.exports = grammar({
   name: "d2",
@@ -59,6 +67,7 @@ module.exports = grammar({
     [$._classes_block],
     [$._classes_item_block],
     [$.class_list],
+    [$.attr_value_list],
     [$._text_block_attrs],
   ],
 
@@ -216,7 +225,7 @@ module.exports = grammar({
 
     // attributes
 
-    _root_attribute: mkBaseAttr(($) => $._root_attr_key),
+    _root_attribute: mkAttr(($) => $._root_attr_key),
 
     _root_attr_key: ($) =>
       choice(
@@ -249,7 +258,10 @@ module.exports = grammar({
 
     _class_name: ($) => alias($.shape_key, $.class_name),
 
-    _base_shape_attribute: mkBaseAttr(($) => $._shape_attr_key),
+    _base_shape_attribute: either(
+      mkListAttr(($) => $._shape_list_attr_key),
+      mkAttr(($) => $._shape_attr_key)
+    ),
 
     _shape_attr_key: ($) =>
       prec(
@@ -260,9 +272,6 @@ module.exports = grammar({
           "label",
           "link",
           "tooltip",
-          // sql
-          "constraint",
-          // image
           "icon",
           "width",
           "height",
@@ -271,6 +280,8 @@ module.exports = grammar({
         )
       ),
 
+    _shape_list_attr_key: ($) => prec(PREC.ATTRIBUTE_KEY, "constraint"),
+
     _style_attribute: ($) =>
       prec(
         PREC.ATTRIBUTE,
@@ -285,7 +296,7 @@ module.exports = grammar({
 
     _style_attribute_block: mkBlock(attrAlias(($) => $._inner_style_attribute)),
 
-    _inner_style_attribute: mkBaseAttr(($) => $._style_attr_key),
+    _inner_style_attribute: mkAttr(($) => $._style_attr_key),
 
     _grid_attr_key: ($) =>
       choice(
@@ -321,7 +332,7 @@ module.exports = grammar({
         "text-transform"
       ),
 
-    _text_shape_attribute: mkBaseAttr(($) => $._text_attr_key),
+    _text_shape_attribute: mkAttr(($) => $._text_attr_key),
 
     _text_attr_key: ($) => "near",
 
@@ -355,6 +366,8 @@ module.exports = grammar({
 
     label: ($) => choice($.string, $._unquoted_string),
 
+    attr_value_list: mkList(($) => $.attr_value),
+
     attr_value: ($) =>
       seq(choice($.boolean, $.integer, $.float, $.string, $._unquoted_string)),
 
@@ -375,7 +388,7 @@ module.exports = grammar({
           token(
             prec(
               PREC.UNQUOTED_STRING,
-              /[^'"`\\|\n\s;{}]([^\\\n;{}]*[^\\\n\s;{}])?/
+              /[^'"`\\|\n\s;{}\[\]]([^\\\n;{}\[\]]*[^\\\n\s;{}\[\]])?/
             )
           )
         )
diff --git a/src/grammar.json b/src/grammar.json
index 3766456..e5db853 100644
--- a/src/grammar.json
+++ b/src/grammar.json
@@ -1251,24 +1251,60 @@
       "value": "class_name"
     },
     "_base_shape_attribute": {
-      "type": "SEQ",
+      "type": "CHOICE",
       "members": [
         {
-          "type": "ALIAS",
-          "content": {
-            "type": "SYMBOL",
-            "name": "_shape_attr_key"
-          },
-          "named": true,
-          "value": "attr_key"
+          "type": "SEQ",
+          "members": [
+            {
+              "type": "ALIAS",
+              "content": {
+                "type": "SYMBOL",
+                "name": "_shape_list_attr_key"
+              },
+              "named": true,
+              "value": "attr_key"
+            },
+            {
+              "type": "SYMBOL",
+              "name": "_colon"
+            },
+            {
+              "type": "CHOICE",
+              "members": [
+                {
+                  "type": "SYMBOL",
+                  "name": "attr_value_list"
+                },
+                {
+                  "type": "SYMBOL",
+                  "name": "attr_value"
+                }
+              ]
+            }
+          ]
         },
         {
-          "type": "SYMBOL",
-          "name": "_colon"
-        },
-        {
-          "type": "SYMBOL",
-          "name": "attr_value"
+          "type": "SEQ",
+          "members": [
+            {
+              "type": "ALIAS",
+              "content": {
+                "type": "SYMBOL",
+                "name": "_shape_attr_key"
+              },
+              "named": true,
+              "value": "attr_key"
+            },
+            {
+              "type": "SYMBOL",
+              "name": "_colon"
+            },
+            {
+              "type": "SYMBOL",
+              "name": "attr_value"
+            }
+          ]
         }
       ]
     },
@@ -1298,10 +1334,6 @@
             "type": "STRING",
             "value": "tooltip"
           },
-          {
-            "type": "STRING",
-            "value": "constraint"
-          },
           {
             "type": "STRING",
             "value": "icon"
@@ -1325,6 +1357,14 @@
         ]
       }
     },
+    "_shape_list_attr_key": {
+      "type": "PREC",
+      "value": 0,
+      "content": {
+        "type": "STRING",
+        "value": "constraint"
+      }
+    },
     "_style_attribute": {
       "type": "PREC",
       "value": 0,
@@ -1843,6 +1883,73 @@
         }
       ]
     },
+    "attr_value_list": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "["
+        },
+        {
+          "type": "REPEAT",
+          "content": {
+            "type": "CHOICE",
+            "members": [
+              {
+                "type": "SYMBOL",
+                "name": "_eol"
+              },
+              {
+                "type": "SEQ",
+                "members": [
+                  {
+                    "type": "SYMBOL",
+                    "name": "attr_value"
+                  },
+                  {
+                    "type": "SYMBOL",
+                    "name": "_end"
+                  }
+                ]
+              }
+            ]
+          }
+        },
+        {
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "SEQ",
+              "members": [
+                {
+                  "type": "SYMBOL",
+                  "name": "attr_value"
+                },
+                {
+                  "type": "CHOICE",
+                  "members": [
+                    {
+                      "type": "SYMBOL",
+                      "name": "_end"
+                    },
+                    {
+                      "type": "BLANK"
+                    }
+                  ]
+                }
+              ]
+            },
+            {
+              "type": "BLANK"
+            }
+          ]
+        },
+        {
+          "type": "STRING",
+          "value": "]"
+        }
+      ]
+    },
     "attr_value": {
       "type": "SEQ",
       "members": [
@@ -1940,7 +2047,7 @@
               "value": -1,
               "content": {
                 "type": "PATTERN",
-                "value": "[^'\"`\\\\|\\n\\s;{}]([^\\\\\\n;{}]*[^\\\\\\n\\s;{}])?"
+                "value": "[^'\"`\\\\|\\n\\s;{}\\[\\]]([^\\\\\\n;{}\\[\\]]*[^\\\\\\n\\s;{}\\[\\]])?"
               }
             }
           }
@@ -2167,6 +2274,9 @@
     [
       "class_list"
     ],
+    [
+      "attr_value_list"
+    ],
     [
       "_text_block_attrs"
     ]
diff --git a/src/node-types.json b/src/node-types.json
index 3974383..212b2f4 100644
--- a/src/node-types.json
+++ b/src/node-types.json
@@ -45,6 +45,21 @@
       ]
     }
   },
+  {
+    "type": "attr_value_list",
+    "named": true,
+    "fields": {},
+    "children": {
+      "multiple": true,
+      "required": false,
+      "types": [
+        {
+          "type": "attr_value",
+          "named": true
+        }
+      ]
+    }
+  },
   {
     "type": "attribute",
     "named": true,
@@ -61,6 +76,10 @@
           "type": "attr_value",
           "named": true
         },
+        {
+          "type": "attr_value_list",
+          "named": true
+        },
         {
           "type": "attribute",
           "named": true
diff --git a/src/parser.c b/src/parser.c
index 2a47b89..561b158 100644
Binary files a/src/parser.c and b/src/parser.c differ
diff --git a/test/corpus/attributes.txt b/test/corpus/attributes.txt
index 542efca..0915414 100644
--- a/test/corpus/attributes.txt
+++ b/test/corpus/attributes.txt
@@ -488,4 +488,30 @@ footer
   (shape (shape_key))
 )
 
+================================================================================
+Declare a attribute with many values
+================================================================================
+block: {
+  constraint: primary_key
+  constraint: [primary_key]
+  constraint: [primary_key; unique]
+  constraint: [
+    primary_key
+    unique
+  ]
+}
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (container
+    (container_key)
+    (block
+      (attribute (attr_key) (attr_value))
+      (attribute (attr_key) (attr_value_list (attr_value)))
+      (attribute (attr_key) (attr_value_list (attr_value) (attr_value)))
+      (attribute (attr_key) (attr_value_list (attr_value) (attr_value)))
+    )
+  )
+)
 
diff --git a/test/corpus/classes.txt b/test/corpus/classes.txt
index a840f96..c29122c 100644
--- a/test/corpus/classes.txt
+++ b/test/corpus/classes.txt
@@ -158,11 +158,22 @@ foo.class: biz
 ================================================================================
 Declare shape with many classes
 ================================================================================
+fee.class: [biz]
 foo.class: [biz; baz]
 
 --------------------------------------------------------------------------------
 
 (source_file
+  (shape
+    (shape_key)
+    (dot)
+    (attribute
+      (keyword_class)
+      (class_list
+        (class_name)
+      )
+    )
+  )
   (shape
     (shape_key)
     (dot)
@@ -181,6 +192,12 @@ Declare a class in the container
 ================================================================================
 foo: {
   class: biz
+  class: [biz]
+  class: [biz; baz]
+  class: [
+    biz
+    baz
+  ]
 }
 
 --------------------------------------------------------------------------------
@@ -193,6 +210,26 @@ foo: {
         (keyword_class)
         (class_name)
       )
+      (attribute
+        (keyword_class)
+        (class_list
+          (class_name)
+        )
+      )
+      (attribute
+        (keyword_class)
+        (class_list
+          (class_name)
+          (class_name)
+        )
+      )
+      (attribute
+        (keyword_class)
+        (class_list
+          (class_name)
+          (class_name)
+        )
+      )
     )
   )
 )
diff --git a/tree-sitter-d2.wasm b/tree-sitter-d2.wasm
index 06e0feb..edec16b 100755
Binary files a/tree-sitter-d2.wasm and b/tree-sitter-d2.wasm differ