diff --git a/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/diagnostics/KotlinToolingDiagnostics.kt b/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/diagnostics/KotlinToolingDiagnostics.kt
index 7bb20954349..8a4632348e6 100644
--- a/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/diagnostics/KotlinToolingDiagnostics.kt
+++ b/libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/diagnostics/KotlinToolingDiagnostics.kt
@@ -583,7 +583,7 @@ object KotlinToolingDiagnostics {
         )
     }
 
-    object KotlinCompilationSourceDeprecation : ToolingDiagnosticFactory(ERROR) {
+    object KotlinCompilationSourceDeprecation : ToolingDiagnosticFactory(WARNING) {
         operator fun invoke(trace: Throwable?) = build(
             """
                 `KotlinCompilation.source(KotlinSourceSet)` method is deprecated 
diff --git a/libraries/tools/kotlin-gradle-plugin/src/functionalTest/resources/expectedDiagnostics/kotlinCompilationSourceDeprecation.txt b/libraries/tools/kotlin-gradle-plugin/src/functionalTest/resources/expectedDiagnostics/kotlinCompilationSourceDeprecation.txt
index 11122e74567..de616f96b23 100644
--- a/libraries/tools/kotlin-gradle-plugin/src/functionalTest/resources/expectedDiagnostics/kotlinCompilationSourceDeprecation.txt
+++ b/libraries/tools/kotlin-gradle-plugin/src/functionalTest/resources/expectedDiagnostics/kotlinCompilationSourceDeprecation.txt
@@ -1,4 +1,4 @@
-[KotlinCompilationSourceDeprecation | ERROR] `KotlinCompilation.source(KotlinSourceSet)` method is deprecated
+[KotlinCompilationSourceDeprecation | WARNING] `KotlinCompilation.source(KotlinSourceSet)` method is deprecated
 and will be removed in upcoming Kotlin releases.
 
 See https://kotl.in/compilation-source-deprecation for details.
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