diff --git a/lib/nodes/Numeric.js b/lib/nodes/Numeric.js
index 5cf25a4..d64dbf2 100644
--- a/lib/nodes/Numeric.js
+++ b/lib/nodes/Numeric.js
@@ -14,7 +14,7 @@ const { registerWalker } = require('../walker');
 
 const Node = require('./Node');
 
-const unitRegex = /%|ch|cm|em|ex|in|mm|pc|pt|px|q|rem|vh|vmax|vmin|vw$/i;
+const unitRegex = /%|ch|cm|em|ex|in|mm|ms|pc|pt|px|s|q|rem|vh|vmax|vmin|vw$/i;
 
 class Numeric extends Node {
   constructor(options = {}) {
diff --git a/test/fixtures/numeric.js b/test/fixtures/numeric.js
index cbedc06..7bf99ae 100644
--- a/test/fixtures/numeric.js
+++ b/test/fixtures/numeric.js
@@ -31,7 +31,12 @@ module.exports = {
     '1E+10',
     '-.567800E-0012780em',
     '.1E-10',
-    '.1E+10'
+    '.1E+10',
+    '0.5s',
+    '500ms',
+    '0.5s + 0.5s',
+    '-.3s',
+    '-.3s + 0.5s'
   ],
   throws: ['+-2.', '.', '.rem', '.2.3rem']
 };
diff --git a/test/snapshots/numeric.test.js.md b/test/snapshots/numeric.test.js.md
index 75986bf..c898dbe 100644
--- a/test/snapshots/numeric.test.js.md
+++ b/test/snapshots/numeric.test.js.md
@@ -1051,3 +1051,292 @@ Generated by [AVA](https://ava.li).
         value: '5',
       },
     ]
+
+## -.3s
+
+> Snapshot 1
+
+    '-.3s'
+
+> Snapshot 2
+
+    '-.3s'
+
+> Snapshot 3
+
+    [
+      Numeric {
+        raws: {
+          after: '',
+          before: '',
+        },
+        source: {
+          end: {
+            column: 1,
+            line: 1,
+          },
+          input: Input {
+            css: '-.3s',
+            hasBOM: false,
+            id: '<input css 26>',
+          },
+          start: {
+            column: 1,
+            line: 1,
+          },
+        },
+        type: 'numeric',
+        unit: 's',
+        value: '-.3',
+      },
+    ]
+
+## -.3s + 0.5s
+
+> Snapshot 1
+
+    '-.3s'
+
+> Snapshot 2
+
+    '-.3s + 0.5s'
+
+> Snapshot 3
+
+    [
+      Numeric {
+        raws: {
+          after: '',
+          before: '',
+        },
+        source: {
+          end: {
+            column: 1,
+            line: 1,
+          },
+          input: Input {
+            css: '-.3s + 0.5s',
+            hasBOM: false,
+            id: '<input css 27>',
+          },
+          start: {
+            column: 1,
+            line: 1,
+          },
+        },
+        type: 'numeric',
+        unit: 's',
+        value: '-.3',
+      },
+      Operator {
+        raws: {
+          after: '',
+          before: ' ',
+        },
+        source: {
+          end: {
+            column: 6,
+            line: 1,
+          },
+          input: Input {
+            css: '-.3s + 0.5s',
+            hasBOM: false,
+            id: '<input css 27>',
+          },
+          start: {
+            column: 6,
+            line: 1,
+          },
+        },
+        type: 'operator',
+        value: '+',
+      },
+      Numeric {
+        raws: {
+          after: '',
+          before: ' ',
+        },
+        source: {
+          end: {
+            column: 8,
+            line: 1,
+          },
+          input: Input {
+            css: '-.3s + 0.5s',
+            hasBOM: false,
+            id: '<input css 27>',
+          },
+          start: {
+            column: 8,
+            line: 1,
+          },
+        },
+        type: 'numeric',
+        unit: 's',
+        value: '0.5',
+      },
+    ]
+
+## 0.5s
+
+> Snapshot 1
+
+    '0.5s'
+
+> Snapshot 2
+
+    '0.5s'
+
+> Snapshot 3
+
+    [
+      Numeric {
+        raws: {
+          after: '',
+          before: '',
+        },
+        source: {
+          end: {
+            column: 1,
+            line: 1,
+          },
+          input: Input {
+            css: '0.5s',
+            hasBOM: false,
+            id: '<input css 23>',
+          },
+          start: {
+            column: 1,
+            line: 1,
+          },
+        },
+        type: 'numeric',
+        unit: 's',
+        value: '0.5',
+      },
+    ]
+
+## 0.5s + 0.5s
+
+> Snapshot 1
+
+    '0.5s'
+
+> Snapshot 2
+
+    '0.5s + 0.5s'
+
+> Snapshot 3
+
+    [
+      Numeric {
+        raws: {
+          after: '',
+          before: '',
+        },
+        source: {
+          end: {
+            column: 1,
+            line: 1,
+          },
+          input: Input {
+            css: '0.5s + 0.5s',
+            hasBOM: false,
+            id: '<input css 25>',
+          },
+          start: {
+            column: 1,
+            line: 1,
+          },
+        },
+        type: 'numeric',
+        unit: 's',
+        value: '0.5',
+      },
+      Operator {
+        raws: {
+          after: '',
+          before: ' ',
+        },
+        source: {
+          end: {
+            column: 6,
+            line: 1,
+          },
+          input: Input {
+            css: '0.5s + 0.5s',
+            hasBOM: false,
+            id: '<input css 25>',
+          },
+          start: {
+            column: 6,
+            line: 1,
+          },
+        },
+        type: 'operator',
+        value: '+',
+      },
+      Numeric {
+        raws: {
+          after: '',
+          before: ' ',
+        },
+        source: {
+          end: {
+            column: 8,
+            line: 1,
+          },
+          input: Input {
+            css: '0.5s + 0.5s',
+            hasBOM: false,
+            id: '<input css 25>',
+          },
+          start: {
+            column: 8,
+            line: 1,
+          },
+        },
+        type: 'numeric',
+        unit: 's',
+        value: '0.5',
+      },
+    ]
+
+## 500ms
+
+> Snapshot 1
+
+    '500ms'
+
+> Snapshot 2
+
+    '500ms'
+
+> Snapshot 3
+
+    [
+      Numeric {
+        raws: {
+          after: '',
+          before: '',
+        },
+        source: {
+          end: {
+            column: 1,
+            line: 1,
+          },
+          input: Input {
+            css: '500ms',
+            hasBOM: false,
+            id: '<input css 24>',
+          },
+          start: {
+            column: 1,
+            line: 1,
+          },
+        },
+        type: 'numeric',
+        unit: 'ms',
+        value: '500',
+      },
+    ]
diff --git a/test/snapshots/numeric.test.js.snap b/test/snapshots/numeric.test.js.snap
index 26556f4..1b85ca3 100644
Binary files a/test/snapshots/numeric.test.js.snap and b/test/snapshots/numeric.test.js.snap differ