diff --git a/src/__tests__/index.js b/src/__tests__/index.js
index d6baba4..cb8321a 100644
--- a/src/__tests__/index.js
+++ b/src/__tests__/index.js
@@ -204,6 +204,12 @@ test(
   '2px'
 )
 
+test(
+  'should not match "calc" in another function signature',
+  testFixture,
+  '-calc(1px + 1px)',
+)
+
 test(
   'should discard zero values (#2) (1)',
   testFixture,
diff --git a/src/index.js b/src/index.js
index d2de067..67f2280 100644
--- a/src/index.js
+++ b/src/index.js
@@ -4,7 +4,7 @@ import { parser } from './parser' // eslint-disable-line
 import reducer from './lib/reducer'
 import stringifier from './lib/stringifier'
 
-const MATCH_CALC = /((?:\-[a-z]+\-)?calc)/
+const MATCH_CALC = /^((?:\-[a-z]+\-)?calc)$/
 
 export default (value, precision = 5) => {
   return valueParser(value).walk(node => {