diff --git a/CHANGELOG.md b/CHANGELOG.md
index a310539..bfedfe2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## next
+
+- Updated `csstree` to [1.0.0-alpha.37](https://github.com/csstree/csstree/releases/tag/v1.0.0-alpha.37)
+
 ## 1.5.1 (October 7, 2019)
 
 - Updated `csstree` to [1.0.0-alpha.34](https://github.com/csstree/csstree/releases/tag/v1.0.0-alpha.34)
diff --git a/package-lock.json b/package-lock.json
index 83a7c9d..1774a10 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -228,12 +228,12 @@
       }
     },
     "css-tree": {
-      "version": "1.0.0-alpha.34",
-      "resolved": "https://registry.npmjs.org/css-tree/-/css-tree-1.0.0-alpha.34.tgz",
-      "integrity": "sha512-JMKJi4h8WkQ+HPjsCUvFnIhGF0I7Jr+J4a+NcHOApyGIBjvx4/hbhk+oKMXydv+OCmVyKBp0hqhHpj5Z61tyMg==",
+      "version": "1.0.0-alpha.37",
+      "resolved": "https://registry.npmjs.org/css-tree/-/css-tree-1.0.0-alpha.37.tgz",
+      "integrity": "sha512-DMxWJg0rnz7UgxKT0Q1HU/L9BeJI0M6ksor0OgqOnF+aRCDWg/N2641HmVyU9KVIu0OVVWOb2IpC9A+BJRnejg==",
       "requires": {
         "mdn-data": "2.0.4",
-        "source-map": "^0.5.3"
+        "source-map": "^0.6.1"
       }
     },
     "debug": {
@@ -1062,9 +1062,9 @@
       }
     },
     "source-map": {
-      "version": "0.5.7",
-      "resolved": "https://registry.npmjs.org/source-map/-/source-map-0.5.7.tgz",
-      "integrity": "sha1-igOdLRAh0i0eoUyA2OpGi6LvP8w="
+      "version": "0.6.1",
+      "resolved": "https://registry.npmjs.org/source-map/-/source-map-0.6.1.tgz",
+      "integrity": "sha512-UjgapumWlbMhkBgzT7Ykc5YXUT46F0iKu8SGXq0bcwP5dz/h0Plj6enJqjz1Zbq2l5WaqYnrVbwWOWMyF3F47g=="
     },
     "sprintf-js": {
       "version": "1.0.3",
diff --git a/package.json b/package.json
index 0416869..ac1764f 100644
--- a/package.json
+++ b/package.json
@@ -23,7 +23,7 @@
   },
   "dependencies": {
     "clap": "^1.1.1",
-    "css-tree": "1.0.0-alpha.34"
+    "css-tree": "1.0.0-alpha.37"
   },
   "devDependencies": {
     "eslint": "^6.3.0",