diff --git a/platform/build-scripts/icons/src/org/jetbrains/intellij/build/images/IconsClassGenerator.kt b/platform/build-scripts/icons/src/org/jetbrains/intellij/build/images/IconsClassGenerator.kt
index 4d9409d9be3a..444e494bcfae 100644
--- a/platform/build-scripts/icons/src/org/jetbrains/intellij/build/images/IconsClassGenerator.kt
+++ b/platform/build-scripts/icons/src/org/jetbrains/intellij/build/images/IconsClassGenerator.kt
@@ -18,6 +18,7 @@ package org.jetbrains.intellij.build.images
 import com.intellij.openapi.util.io.FileUtil
 import com.intellij.openapi.util.text.StringUtil
 import com.intellij.util.containers.ContainerUtil
+import com.intellij.util.diff.Diff
 import org.jetbrains.jps.model.JpsSimpleElement
 import org.jetbrains.jps.model.java.JavaSourceRootProperties
 import org.jetbrains.jps.model.java.JavaSourceRootType
@@ -29,7 +30,7 @@ import java.util.*
 class IconsClassGenerator(val projectHome: File, val util: JpsModule, val writeChangesToDisk: Boolean = true) {
   private var processedClasses = 0
   private var processedIcons = 0
-  private var modifiedClasses = ArrayList<Pair<JpsModule, File>>()
+  private var modifiedClasses = ArrayList<Triple<JpsModule, File, String>>()
 
   fun processModule(module: JpsModule) {
     val customLoad: Boolean
@@ -81,13 +82,30 @@ class IconsClassGenerator(val projectHome: File, val util: JpsModule, val writeC
       processedClasses++
 
       if (!outFile.exists() || outFile.readText().lines() != text.lines()) {
-        modifiedClasses.add(Pair(module, outFile))
-
         if (writeChangesToDisk) {
           outFile.parentFile.mkdirs()
           outFile.writeText(text)
           println("Updated icons class: ${outFile.name}")
         }
+        else {
+          val oldLines = outFile.readText().lines()
+          val newLines = text.lines()
+
+          val sb = StringBuilder()
+          var ch = Diff.buildChanges(oldLines.toTypedArray(), newLines.toTypedArray())
+          while (ch != null) {
+            val deleted = oldLines.subList(ch.line0, ch.line0 + ch.deleted)
+            val inserted = newLines.subList(ch.line1, ch.line1 + ch.inserted)
+
+            if (sb.isNotEmpty()) sb.append("=".repeat(20)).append("\n")
+            deleted.forEach { sb.append("-").append(it).append("\n") }
+            inserted.forEach { sb.append("+").append(it).append("\n") }
+
+            ch = ch.link
+          }
+
+          modifiedClasses.add(Triple(module, outFile, sb.toString()))
+        }
       }
     }
   }
diff --git a/platform/build-scripts/icons/tests/org/jetbrains/intellij/build/images/ImageResourcesTest.kt b/platform/build-scripts/icons/tests/org/jetbrains/intellij/build/images/ImageResourcesTest.kt
index efa424df9287..022169d910ce 100644
--- a/platform/build-scripts/icons/tests/org/jetbrains/intellij/build/images/ImageResourcesTest.kt
+++ b/platform/build-scripts/icons/tests/org/jetbrains/intellij/build/images/ImageResourcesTest.kt
@@ -220,22 +220,22 @@ private class MyIconClassFileChecker(val projectHome: File, val util: JpsModule)
     val generator = IconsClassGenerator(projectHome, util, false)
     generator.processModule(module)
 
-    generator.getModifiedClasses().forEach { (module, file) ->
-      failures.add(FailedTest(module, "image class file should be regenerated", file))
+    generator.getModifiedClasses().forEach { (module, file, details) ->
+      failures.add(FailedTest(module, "image class file should be regenerated", file, details))
     }
   }
 }
 
-class FailedTest internal constructor(val module: String, val message: String, val id: String, val paths: List<String>) {
+class FailedTest internal constructor(val module: String, val message: String, val id: String, val details: String) {
   internal constructor(module: JpsModule, message: String, image: ImagePaths, file: File) :
-    this(module.name, message, image.id, listOf(file.absolutePath))
+    this(module.name, message, image.id, file.absolutePath)
 
   internal constructor(module: JpsModule, message: String, image: ImagePaths) :
-    this(module.name, message, image.id, image.files.map { it.absolutePath }.toList())
+    this(module.name, message, image.id, image.files.map { it.absolutePath }.joinToString("\n"))
 
-  internal constructor(module: JpsModule, message: String, file: File) :
-    this(module.name, message, file.name, listOf(file.path))
+  internal constructor(module: JpsModule, message: String, file: File, details: String) :
+    this(module.name, message, file.name, "${file.path}\n\n$details")
 
   fun getTestName(): String = "'${module}' - $id - $message"
-  fun getException(): Throwable = Exception("${message}\n\n${paths.joinToString("\n")}")
+  fun getException(): Throwable = Exception("${message}\n\n$details".trim())
 }
\ No newline at end of file