diff --git a/Changelog.md b/Changelog.md
index 5fc49b1083f..e6d03d890e5 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -33,6 +33,7 @@
 - Add kotlinClassName() and kotlinFunctionName() macros for use in live templates
 - Complete private members from libraries in Evaluate Expression dialog
 - Show error message when debug info for some local variable is corrupted
+- [KT-11638](https://youtrack.jetbrains.com/issue/KT-11638) Fixed hashCode() implementation in "Generate equals/hashCode" action
 
 ## 1.0.1-2
 
diff --git a/idea/src/org/jetbrains/kotlin/idea/actions/generate/KotlinGenerateEqualsAndHashcodeAction.kt b/idea/src/org/jetbrains/kotlin/idea/actions/generate/KotlinGenerateEqualsAndHashcodeAction.kt
index a91ae7e49a5..60edc0be578 100644
--- a/idea/src/org/jetbrains/kotlin/idea/actions/generate/KotlinGenerateEqualsAndHashcodeAction.kt
+++ b/idea/src/org/jetbrains/kotlin/idea/actions/generate/KotlinGenerateEqualsAndHashcodeAction.kt
@@ -221,7 +221,7 @@ class KotlinGenerateEqualsAndHashcodeAction : KotlinGenerateMemberActionBase<Kot
                 val resultVarName = KotlinNameSuggester.suggestNameByName("result", validator)
                 StringBuilder().apply {
                     append("var $resultVarName = $initialValue\n")
-                    propertyIterator.forEach { append("$resultVarName += 31 * $resultVarName + ${it.genVariableHashCode(true)}\n") }
+                    propertyIterator.forEach { append("$resultVarName = 31 * $resultVarName + ${it.genVariableHashCode(true)}\n") }
                     append("return $resultVarName")
                 }.toString()
             } else "return $initialValue"
diff --git a/idea/testData/codeInsight/generate/equalsWithHashCode/arrays.kt.after b/idea/testData/codeInsight/generate/equalsWithHashCode/arrays.kt.after
index cc128145e6d..68afca06f34 100644
--- a/idea/testData/codeInsight/generate/equalsWithHashCode/arrays.kt.after
+++ b/idea/testData/codeInsight/generate/equalsWithHashCode/arrays.kt.after
@@ -22,8 +22,8 @@ class A(val n: IntArray, val s: Array<String>) {
 
     override fun hashCode(): Int{
         var result = Arrays.hashCode(n)
-        result += 31 * result + Arrays.hashCode(s)
-        result += 31 * result + f.hashCode()
+        result = 31 * result + Arrays.hashCode(s)
+        result = 31 * result + f.hashCode()
         return result
     }
 }
\ No newline at end of file
diff --git a/idea/testData/codeInsight/generate/equalsWithHashCode/multipleVars.kt.after b/idea/testData/codeInsight/generate/equalsWithHashCode/multipleVars.kt.after
index ae50339c5d1..36e75ab4ec6 100644
--- a/idea/testData/codeInsight/generate/equalsWithHashCode/multipleVars.kt.after
+++ b/idea/testData/codeInsight/generate/equalsWithHashCode/multipleVars.kt.after
@@ -20,8 +20,8 @@ class A(val n: Int, val s: String) {
 
     override fun hashCode(): Int{
         var result = n
-        result += 31 * result + s.hashCode()
-        result += 31 * result + f.hashCode()
+        result = 31 * result + s.hashCode()
+        result = 31 * result + f.hashCode()
         return result
     }
 }
\ No newline at end of file
diff --git a/idea/testData/codeInsight/generate/equalsWithHashCode/multipleVarsNullable.kt.after b/idea/testData/codeInsight/generate/equalsWithHashCode/multipleVarsNullable.kt.after
index 32f1d9b67d1..dc5e0f1a7e5 100644
--- a/idea/testData/codeInsight/generate/equalsWithHashCode/multipleVarsNullable.kt.after
+++ b/idea/testData/codeInsight/generate/equalsWithHashCode/multipleVarsNullable.kt.after
@@ -20,8 +20,8 @@ class A(val n: Int?, val s: String) {
 
     override fun hashCode(): Int{
         var result = n ?: 0
-        result += 31 * result + s.hashCode()
-        result += 31 * result + (f?.hashCode() ?: 0)
+        result = 31 * result + s.hashCode()
+        result = 31 * result + (f?.hashCode() ?: 0)
         return result
     }
 }
\ No newline at end of file
diff --git a/idea/testData/codeInsight/generate/equalsWithHashCode/multipleVarsWithSuperClass.kt.after b/idea/testData/codeInsight/generate/equalsWithHashCode/multipleVarsWithSuperClass.kt.after
index e409bb30dc8..9d793886423 100644
--- a/idea/testData/codeInsight/generate/equalsWithHashCode/multipleVarsWithSuperClass.kt.after
+++ b/idea/testData/codeInsight/generate/equalsWithHashCode/multipleVarsWithSuperClass.kt.after
@@ -26,9 +26,9 @@ class A(val n: Int, val s: String) : X() {
 
     override fun hashCode(): Int{
         var result = super.hashCode()
-        result += 31 * result + n
-        result += 31 * result + s.hashCode()
-        result += 31 * result + f.hashCode()
+        result = 31 * result + n
+        result = 31 * result + s.hashCode()
+        result = 31 * result + f.hashCode()
         return result
     }
 }
\ No newline at end of file
diff --git a/idea/testData/codeInsight/generate/equalsWithHashCode/nameClash.kt.after b/idea/testData/codeInsight/generate/equalsWithHashCode/nameClash.kt.after
index 0520eb4d71b..0c0263d67d4 100644
--- a/idea/testData/codeInsight/generate/equalsWithHashCode/nameClash.kt.after
+++ b/idea/testData/codeInsight/generate/equalsWithHashCode/nameClash.kt.after
@@ -17,7 +17,7 @@ class A(val result: Int, val s: String) {
 
     override fun hashCode(): Int{
         var result1 = result
-        result1 += 31 * result1 + s.hashCode()
+        result1 = 31 * result1 + s.hashCode()
         return result1
     }
 }
\ No newline at end of file
diff --git a/idea/testData/codeInsight/generate/equalsWithHashCode/nullableArrays.kt.after b/idea/testData/codeInsight/generate/equalsWithHashCode/nullableArrays.kt.after
index 69c4aa14f20..94897f0ec00 100644
--- a/idea/testData/codeInsight/generate/equalsWithHashCode/nullableArrays.kt.after
+++ b/idea/testData/codeInsight/generate/equalsWithHashCode/nullableArrays.kt.after
@@ -22,8 +22,8 @@ class A(val n: IntArray?, val s: Array<String>?) {
 
     override fun hashCode(): Int{
         var result = n?.let { Arrays.hashCode(it) } ?: 0
-        result += 31 * result + (s?.let { Arrays.hashCode(it) } ?: 0)
-        result += 31 * result + f.hashCode()
+        result = 31 * result + (s?.let { Arrays.hashCode(it) } ?: 0)
+        result = 31 * result + f.hashCode()
         return result
     }
 }
\ No newline at end of file
diff --git a/idea/testData/codeInsight/generate/equalsWithHashCode/singleVarWithJavaSuperClass.kt.after b/idea/testData/codeInsight/generate/equalsWithHashCode/singleVarWithJavaSuperClass.kt.after
index 6f530d7417e..4cf6708665e 100644
--- a/idea/testData/codeInsight/generate/equalsWithHashCode/singleVarWithJavaSuperClass.kt.after
+++ b/idea/testData/codeInsight/generate/equalsWithHashCode/singleVarWithJavaSuperClass.kt.after
@@ -17,7 +17,7 @@ class A(val n: Int) : X() {
 
     override fun hashCode(): Int{
         var result = super.hashCode()
-        result += 31 * result + n
+        result = 31 * result + n
         return result
     }
 }
\ No newline at end of file
diff --git a/idea/testData/codeInsight/generate/equalsWithHashCode/singleVarWithSuperClass.kt.after b/idea/testData/codeInsight/generate/equalsWithHashCode/singleVarWithSuperClass.kt.after
index 0ec827ce992..4d7a1bb5140 100644
--- a/idea/testData/codeInsight/generate/equalsWithHashCode/singleVarWithSuperClass.kt.after
+++ b/idea/testData/codeInsight/generate/equalsWithHashCode/singleVarWithSuperClass.kt.after
@@ -22,7 +22,7 @@ class A(val n: Int) : X() {
 
     override fun hashCode(): Int{
         var result = super.hashCode()
-        result += 31 * result + n
+        result = 31 * result + n
         return result
     }
 }
\ No newline at end of file