diff --git a/lib/compiler/passes/generate-bytecode.js b/lib/compiler/passes/generate-bytecode.js
index 7bf673e..b0c1c8f 100644
--- a/lib/compiler/passes/generate-bytecode.js
+++ b/lib/compiler/passes/generate-bytecode.js
@@ -575,7 +575,7 @@ function generateBytecode(ast) {
         regexp = '/^['
           + (node.inverted ? '^' : '')
           + node.parts.map(function(part) {
-              return part instanceof Array
+              return Array.isArray(part)
                 ? js.regexpClassEscape(part[0])
                   + '-'
                   + js.regexpClassEscape(part[1])
@@ -592,7 +592,7 @@ function generateBytecode(ast) {
 
       parts = '['
         + node.parts.map(function(part) {
-            return part instanceof Array
+            return Array.isArray(part)
               ? '["' + js.stringEscape(part[0]) + '", "' + js.stringEscape(part[1]) + '"]'
               : '"' + js.stringEscape(part) + '"';
           }).join(', ')
diff --git a/lib/compiler/passes/generate-js.js b/lib/compiler/passes/generate-js.js
index 5f34c29..82d1ea4 100644
--- a/lib/compiler/passes/generate-js.js
+++ b/lib/compiler/passes/generate-js.js
@@ -790,7 +790,7 @@ function generateJS(ast, options) {
       '              i;',
       '',
       '          for (i = 0; i < expectation.parts.length; i++) {',
-      '            escapedParts += expectation.parts[i] instanceof Array',
+      '            escapedParts += Array.isArray(expectation.parts[i])',
       '              ? classEscape(expectation.parts[i][0]) + "-" + classEscape(expectation.parts[i][1])',
       '              : classEscape(expectation.parts[i]);',
       '          }',
diff --git a/lib/parser.js b/lib/parser.js
index 429dc84..5337aa7 100644
--- a/lib/parser.js
+++ b/lib/parser.js
@@ -40,7 +40,7 @@ peg$SyntaxError.buildMessage = function(expected, found) {
               i;
 
           for (i = 0; i < expectation.parts.length; i++) {
-            escapedParts += expectation.parts[i] instanceof Array
+            escapedParts += Array.isArray(expectation.parts[i])
               ? classEscape(expectation.parts[i][0]) + "-" + classEscape(expectation.parts[i][1])
               : classEscape(expectation.parts[i]);
           }