diff --git a/index.js b/index.js
index f5105a6..3ec7247 100755
--- a/index.js
+++ b/index.js
@@ -106,6 +106,9 @@ function reduceCSSCalc(value, decimalPrecision) {
    * @returns {String}
    */
   function evaluateNestedExpression(expression, call) {
+    // Remove the calc part from nested expressions to ensure
+    // better browser compatibility
+    expression = expression.replace(/((?:\-[a-z]+\-)?calc)/g, "")
     var evaluatedPart = ""
     var nonEvaluatedPart = expression
     var matches
diff --git a/test/index.js b/test/index.js
index f8c7164..7425e22 100755
--- a/test/index.js
+++ b/test/index.js
@@ -103,7 +103,7 @@ test("ignore unrecognized values", function(t) {
   t.equal(reduceCSSCalc("calc((4px + 8px) + (--foo) + (10% * 20%))"), "calc(12px + (--foo) + 2%)", "ignore unrecognized part between parenthesis")
   t.equal(reduceCSSCalc("calc((4px + 8px) + var(--foo) + (10% * 20%))"), "calc(12px + var(--foo) + 2%)", "ignore unrecognized function")
 
-  t.equal(reduceCSSCalc("calc(calc(4px + 8px) + calc(var(--foo) + 10px) + calc(10% * 20%))"), "calc(12px + calc(var(--foo) + 10px) + 2%)", "ignore unrecognized nested call")
+  t.equal(reduceCSSCalc("calc(calc(4px + 8px) + calc(var(--foo) + 10px) + calc(10% * 20%))"), "calc(12px + (var(--foo) + 10px) + 2%)", "ignore unrecognized nested call")
 
   t.equal(reduceCSSCalc("calc(100% - var(--my-var))"), "calc(100% - var(--my-var))", "should not try to reduce 100% - var");
   t.end()
@@ -127,3 +127,10 @@ test("should handle calc() with values without leading 0", function(t) {
   t.equal(reduceCSSCalc("calc(.1 + .1 + 1.1 + 0.2)"), "1.5", "addition")
   t.end()
 })
+
+test("should remove calc from unresolved nested expressions", function(t) {
+  t.equal(reduceCSSCalc("-webkit-calc(21vh + -webkit-calc(21vh + 80px * 1/3 + 5px) + -webkit-calc(10vw + 80px * 2/3))"), "-webkit-calc(21vh + (21vh + 80px * 1/3 + 5px) + (10vw + 80px * 2/3))")
+  t.equal(reduceCSSCalc("-moz-calc(21vh + -moz-calc(21vh + 80px * 1/3 + 5px) + -moz-calc(10vw + 80px * 2/3))"), "-moz-calc(21vh + (21vh + 80px * 1/3 + 5px) + (10vw + 80px * 2/3))")
+  t.equal(reduceCSSCalc("calc(21vh + calc(21vh + 80px * 1/3 + 5px) + calc(10vw + 80px * 2/3))"), "calc(21vh + (21vh + 80px * 1/3 + 5px) + (10vw + 80px * 2/3))")
+  t.end()
+})