diff --git a/CHANGELOG.md b/CHANGELOG.md
index e194f767..bf172df5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,16 @@
 
 All notable changes to this project will be documented in this file. See [standard-version](https://github.com/conventional-changelog/standard-version) for commit guidelines.
 
+<a name="4.2.1"></a>
+## [4.2.1](https://github.com/yargs/yargs-parser/compare/v4.2.0...v4.2.1) (2017-01-02)
+
+
+### Bug Fixes
+
+* flatten/duplicate regression ([#75](https://github.com/yargs/yargs-parser/issues/75)) ([68d68a0](https://github.com/yargs/yargs-parser/commit/68d68a0))
+
+
+
 <a name="4.2.0"></a>
 # [4.2.0](https://github.com/yargs/yargs-parser/compare/v4.1.0...v4.2.0) (2016-12-01)
 
diff --git a/index.js b/index.js
index cdb5fc55..1a04d559 100644
--- a/index.js
+++ b/index.js
@@ -325,8 +325,10 @@ function parse (args, opts) {
       i = ii
       argsToSet.push(args[ii])
     }
-    if (multipleArrayFlag && !configuration['flatten-duplicate-arrays']) {
-      setArg(key, argsToSet)
+    if (multipleArrayFlag) {
+      setArg(key, argsToSet.map(function (arg) {
+        return processValue(key, arg)
+      }))
     } else {
       argsToSet.forEach(function (arg) {
         setArg(key, arg)
@@ -339,33 +341,13 @@ function parse (args, opts) {
   function setArg (key, val) {
     unsetDefaulted(key)
 
-    // handle parsing boolean arguments --foo=true --bar false.
-    if (checkAllAliases(key, flags.bools) || checkAllAliases(key, flags.counts)) {
-      if (typeof val === 'string') val = val === 'true'
-    }
-
     if (/-/.test(key) && !(flags.aliases[key] && flags.aliases[key].length) && configuration['camel-case-expansion']) {
       var c = camelCase(key)
       flags.aliases[key] = [c]
       newAliases[c] = true
     }
 
-    var value = val
-    if (!checkAllAliases(key, flags.strings) && !checkAllAliases(key, flags.coercions)) {
-      if (isNumber(val)) value = Number(val)
-      if (!isUndefined(val) && !isNumber(val) && checkAllAliases(key, flags.numbers)) value = NaN
-    }
-
-    // increment a count given as arg (either no value or value parsed as boolean)
-    if (checkAllAliases(key, flags.counts) && (isUndefined(value) || typeof value === 'boolean')) {
-      value = increment
-    }
-
-    // Set normalized value when key is in 'normalize' and in 'arrays'
-    if (checkAllAliases(key, flags.normalize) && checkAllAliases(key, flags.arrays)) {
-      if (Array.isArray(val)) value = val.map(path.normalize)
-      else value = path.normalize(val)
-    }
+    var value = processValue(key, val)
 
     var splitKey = key.split('.')
     setKey(argv, splitKey, value)
@@ -407,6 +389,31 @@ function parse (args, opts) {
     }
   }
 
+  function processValue (key, val) {
+    // handle parsing boolean arguments --foo=true --bar false.
+    if (checkAllAliases(key, flags.bools) || checkAllAliases(key, flags.counts)) {
+      if (typeof val === 'string') val = val === 'true'
+    }
+
+    var value = val
+    if (!checkAllAliases(key, flags.strings) && !checkAllAliases(key, flags.coercions)) {
+      if (isNumber(val)) value = Number(val)
+      if (!isUndefined(val) && !isNumber(val) && checkAllAliases(key, flags.numbers)) value = NaN
+    }
+
+    // increment a count given as arg (either no value or value parsed as boolean)
+    if (checkAllAliases(key, flags.counts) && (isUndefined(value) || typeof value === 'boolean')) {
+      value = increment
+    }
+
+    // Set normalized value when key is in 'normalize' and in 'arrays'
+    if (checkAllAliases(key, flags.normalize) && checkAllAliases(key, flags.arrays)) {
+      if (Array.isArray(val)) value = val.map(path.normalize)
+      else value = path.normalize(val)
+    }
+    return value
+  }
+
   // set args from config.json file, this should be
   // applied last so that defaults can be applied.
   function setConfig (argv) {
@@ -551,15 +558,23 @@ function parse (args, opts) {
 
     var key = keys[keys.length - 1]
 
+    var isTypeArray = checkAllAliases(key, flags.arrays)
+    var isValueArray = Array.isArray(value)
+    var duplicate = configuration['duplicate-arguments-array']
+
     if (value === increment) {
       o[key] = increment(o[key])
-    } else if (o[key] === undefined && checkAllAliases(key, flags.arrays)) {
-      o[key] = Array.isArray(value) && configuration['flatten-duplicate-arrays'] ? value : [value]
-    } else if (o[key] === undefined || checkAllAliases(key, flags.bools) || checkAllAliases(keys.join('.'), flags.bools) || checkAllAliases(key, flags.counts)) {
-      o[key] = value
     } else if (Array.isArray(o[key])) {
-      o[key].push(value)
-    } else if (configuration['duplicate-arguments-array']) {
+      if (duplicate && isTypeArray && isValueArray) {
+        o[key] = configuration['flatten-duplicate-arrays'] ? o[key].concat(value) : [o[key]].concat([value])
+      } else if (!duplicate && Boolean(isTypeArray) === Boolean(isValueArray)) {
+        o[key] = value
+      } else {
+        o[key] = o[key].concat([value])
+      }
+    } else if (o[key] === undefined && isTypeArray) {
+      o[key] = isValueArray ? value : [value]
+    } else if (duplicate && !(o[key] === undefined || checkAllAliases(key, flags.bools) || checkAllAliases(keys.join('.'), flags.bools) || checkAllAliases(key, flags.counts))) {
       o[key] = [ o[key], value ]
     } else {
       o[key] = value
diff --git a/package.json b/package.json
index 953897e2..9b3ddd55 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "yargs-parser",
-  "version": "4.2.0",
+  "version": "4.2.1",
   "description": "the mighty option parser used by yargs",
   "main": "index.js",
   "scripts": {
@@ -31,7 +31,7 @@
     "mocha": "^3.0.1",
     "nyc": "^10.0.0",
     "standard": "^8.0.0",
-    "standard-version": "^3.0.0"
+    "standard-version": "^4.0.0"
   },
   "dependencies": {
     "camelcase": "^3.0.0"
diff --git a/test/yargs-parser.js b/test/yargs-parser.js
index 5d4243aa..c9c59993 100644
--- a/test/yargs-parser.js
+++ b/test/yargs-parser.js
@@ -1374,11 +1374,16 @@ describe('yargs-parser', function () {
   })
 
   describe('array', function () {
-    it('should group values into an array if the same option is specified multiple times', function () {
-      var parse = parser(['-v', 'a', '-v', 'b', '-v', 'c'])
+    it('should group values into an array if the same option is specified multiple times (duplicate-arguments-array=true)', function () {
+      var parse = parser(['-v', 'a', '-v', 'b', '-v', 'c'], {configuration: {'duplicate-arguments-array': true}})
       parse.should.have.property('v').and.deep.equal(['a', 'b', 'c'])
       parse.should.have.property('_').with.length(0)
     })
+    it('should keep only the last value if the same option is specified multiple times (duplicate-arguments-false)', function () {
+      var parse = parser(['-v', 'a', '-v', 'b', '-v', 'c'], {configuration: {'duplicate-arguments-array': false}})
+      parse.should.have.property('v').and.equal('c')
+      parse.should.have.property('_').with.length(0)
+    })
 
     it('should default an array to an empty array if passed as first option followed by another', function () {
       var result = parser(['-a', '-b'], {
@@ -2012,6 +2017,182 @@ describe('yargs-parser', function () {
         parsed['x'].should.deep.equal(['a', 'b'])
       })
     })
+
+    describe('duplicate-arguments-array VS flatten-duplicate-arrays', function () {
+      /*
+        duplicate=false, flatten=false
+          type=array
+            [-x 1 2 3]          => [1, 2, 3]
+            [-x 1 2 3 -x 2 3 4] => [2, 3, 4]
+          type=string/number/etc
+            [-x 1 -x 2 -x 3]    => 3
+
+        duplicate=false, flatten=true
+          type=array
+            [-x 1 2 3]          => [1, 2, 3]
+            [-x 1 2 3 -x 2 3 4] => [2, 3, 4]
+          type=string/number/etc
+            [-x 1 -x 2 -x 3]    => 3
+
+        duplicate=true, flatten=true
+          type=array
+            [-x 1 2 3]          => [1, 2, 3]
+            [-x 1 2 3 -x 2 3 4] => [1, 2, 3, 2, 3, 4]
+          type=string/number/etc
+            [-x 1 -x 2 -x 3]    => [1, 2, 3]
+
+        duplicate=true, flatten=false
+          type=array
+            [-x 1 2 3]          => [1, 2, 3]
+            [-x 1 2 3 -x 2 3 4] => [[1, 2, 3], [2, 3, 4]]
+          type=string/number/etc
+            [-x 1 -x 2 -x 3]    => [1, 2, 3]
+      */
+      describe('duplicate=false, flatten=false,', function () {
+        describe('type=array', function () {
+          it('[-x 1 2 3] => [1, 2, 3]', function () {
+            var parsed = parser('-x 1 2 3', {
+              array: ['x'],
+              configuration: {
+                'duplicate-arguments-array': false,
+                'flatten-duplicate-arrays': false
+              }
+            })
+            parsed['x'].should.deep.equal([1, 2, 3])
+          })
+          it('[-x 1 2 3 -x 2 3 4] => [2, 3, 4]', function () {
+            var parsed = parser('-x 1 2 3 -x 2 3 4', {
+              array: ['x'],
+              configuration: {
+                'duplicate-arguments-array': false,
+                'flatten-duplicate-arrays': false
+              }
+            })
+            parsed['x'].should.deep.equal([2, 3, 4])
+          })
+        })
+        describe('type=number', function () {
+          it('[-x 1 -x 2 -x 3] => 3', function () {
+            var parsed = parser('-x 1 -x 2 -x 3', {
+              number: 'x',
+              configuration: {
+                'duplicate-arguments-array': false,
+                'flatten-duplicate-arrays': false
+              }
+            })
+            parsed['x'].should.deep.equal(3)
+          })
+        })
+      })
+      describe('duplicate=false, flatten=true,', function () {
+        describe('type=array', function () {
+          it('[-x 1 2 3] => [1, 2, 3]', function () {
+            var parsed = parser('-x 1 2 3', {
+              array: ['x'],
+              configuration: {
+                'duplicate-arguments-array': false,
+                'flatten-duplicate-arrays': true
+              }
+            })
+            parsed['x'].should.deep.equal([1, 2, 3])
+          })
+          it('[-x 1 2 3 -x 2 3 4] => [2, 3, 4]', function () {
+            var parsed = parser('-x 1 2 3 -x 2 3 4', {
+              array: ['x'],
+              configuration: {
+                'duplicate-arguments-array': false,
+                'flatten-duplicate-arrays': true
+              }
+            })
+            parsed['x'].should.deep.equal([2, 3, 4])
+          })
+        })
+        describe('type=number', function () {
+          it('[-x 1 -x 2 -x 3] => 3', function () {
+            var parsed = parser('-x 1 -x 2 -x 3', {
+              number: 'x',
+              configuration: {
+                'duplicate-arguments-array': false,
+                'flatten-duplicate-arrays': true
+              }
+            })
+            parsed['x'].should.deep.equal(3)
+          })
+        })
+      })
+      describe('duplicate=true, flatten=true,', function () {
+        describe('type=array', function () {
+          it('[-x 1 2 3] => [1, 2, 3]', function () {
+            var parsed = parser('-x 1 2 3', {
+              array: ['x'],
+              configuration: {
+                'duplicate-arguments-array': true,
+                'flatten-duplicate-arrays': true
+              }
+            })
+            parsed['x'].should.deep.equal([1, 2, 3])
+          })
+          it('[-x 1 2 3 -x 2 3 4] => [1, 2, 3, 2, 3, 4]', function () {
+            var parsed = parser('-x 1 2 3 -x 2 3 4', {
+              array: ['x'],
+              configuration: {
+                'duplicate-arguments-array': true,
+                'flatten-duplicate-arrays': true
+              }
+            })
+            parsed['x'].should.deep.equal([1, 2, 3, 2, 3, 4])
+          })
+        })
+        describe('type=number', function () {
+          it('[-x 1 -x 2 -x 3] => [1, 2, 3]', function () {
+            var parsed = parser('-x 1 -x 2 -x 3', {
+              number: 'x',
+              configuration: {
+                'duplicate-arguments-array': true,
+                'flatten-duplicate-arrays': true
+              }
+            })
+            parsed['x'].should.deep.equal([1, 2, 3])
+          })
+        })
+      })
+      describe('duplicate=true, flatten=false,', function () {
+        describe('type=array', function () {
+          it('[-x 1 -x 2 -x 3] => [1, 2, 3]', function () {
+            var parsed = parser('-x 1 -x 2 -x 3', {
+              array: ['x'],
+              configuration: {
+                'duplicate-arguments-array': true,
+                'flatten-duplicate-arrays': false
+              }
+            })
+            parsed['x'].should.deep.equal([1, 2, 3])
+          })
+          it('[-x 1 2 3 -x 2 3 4] => [[1, 2, 3], [ 2, 3, 4]]', function () {
+            var parsed = parser('-x 1 2 3 -x 2 3 4', {
+              array: ['x'],
+              configuration: {
+                'duplicate-arguments-array': true,
+                'flatten-duplicate-arrays': false
+              }
+            })
+            parsed['x'].should.deep.equal([[1, 2, 3], [2, 3, 4]])
+          })
+        })
+        describe('type=number', function () {
+          it('[-x 1 -x 2 -x 3] => [1, 2, 3]', function () {
+            var parsed = parser('-x 1 -x 2 -x 3', {
+              number: 'x',
+              configuration: {
+                'duplicate-arguments-array': true,
+                'flatten-duplicate-arrays': false
+              }
+            })
+            parsed['x'].should.deep.equal([1, 2, 3])
+          })
+        })
+      })
+    })
   })
 
   // addresses: https://github.com/yargs/yargs-parser/issues/41