diff --git a/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/ConfigurationCacheIT.kt b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/ConfigurationCacheIT.kt
index 3f4b957c3e7..05718a45a98 100644
--- a/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/ConfigurationCacheIT.kt
+++ b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/ConfigurationCacheIT.kt
@@ -66,6 +66,17 @@ class ConfigurationCacheIT : AbstractConfigurationCacheIT() {
         testConfigurationCacheOf("assemble", executedTaskNames = asList(":lib-project:compileKotlin"))
     }
 
+    // KT-43605
+    @Test
+    fun testInstantExecutionWithBuildSrc() = with(Project("instantExecutionWithBuildSrc")) {
+        setupWorkingDir()
+        testConfigurationCacheOf(
+            "build", executedTaskNames = listOf(
+                ":compileKotlin",
+            )
+        )
+    }
+
     @Test
     fun testInstantExecutionForJs() = with(Project("instantExecutionToJs")) {
         testConfigurationCacheOf("assemble", executedTaskNames = asList(":compileKotlin2Js"))
diff --git a/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/instantExecutionWithBuildSrc/build.gradle b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/instantExecutionWithBuildSrc/build.gradle
new file mode 100644
index 00000000000..1ac0584922f
--- /dev/null
+++ b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/instantExecutionWithBuildSrc/build.gradle
@@ -0,0 +1,16 @@
+buildscript {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+    }
+    dependencies {
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+apply plugin: 'kotlin'
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
\ No newline at end of file
diff --git a/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/instantExecutionWithBuildSrc/buildSrc/build.gradle b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/instantExecutionWithBuildSrc/buildSrc/build.gradle
new file mode 100644
index 00000000000..9f9f07c57cd
--- /dev/null
+++ b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/instantExecutionWithBuildSrc/buildSrc/build.gradle
@@ -0,0 +1,16 @@
+buildscript {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+    }
+    dependencies {
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+apply plugin: 'kotlin'
\ No newline at end of file
diff --git a/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/instantExecutionWithBuildSrc/buildSrc/src/main/kotlin/build.kt b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/instantExecutionWithBuildSrc/buildSrc/src/main/kotlin/build.kt
new file mode 100644
index 00000000000..59281f1b0bb
--- /dev/null
+++ b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/instantExecutionWithBuildSrc/buildSrc/src/main/kotlin/build.kt
@@ -0,0 +1 @@
+fun foo() {}
\ No newline at end of file
diff --git a/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/instantExecutionWithBuildSrc/src/main/kotlin/Hello.kt b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/instantExecutionWithBuildSrc/src/main/kotlin/Hello.kt
new file mode 100644
index 00000000000..65490fbf75f
--- /dev/null
+++ b/libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/resources/testProject/instantExecutionWithBuildSrc/src/main/kotlin/Hello.kt
@@ -0,0 +1 @@
+fun hello() = "Hello"
\ No newline at end of file