diff --git a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
index 3d43ecceae8..d584772346f 100644
--- a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
+++ b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
@@ -77,16 +77,16 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
         val FLOAT_LITERAL_OUT_OF_RANGE by error<PsiElement>()
         val WRONG_LONG_SUFFIX by error<KtElement>(PositioningStrategy.LONG_LITERAL_SUFFIX)
         val DIVISION_BY_ZERO by warning<KtExpression>()
-        val VAL_OR_VAR_ON_LOOP_PARAMETER by warning<KtParameter>(PositioningStrategy.VAL_OR_VAR_NODE) {
+        val VAL_OR_VAR_ON_LOOP_PARAMETER by error<KtParameter>(PositioningStrategy.VAL_OR_VAR_NODE) {
             parameter<KtKeywordToken>("valOrVar")
         }
-        val VAL_OR_VAR_ON_FUN_PARAMETER by warning<KtParameter>(PositioningStrategy.VAL_OR_VAR_NODE) {
+        val VAL_OR_VAR_ON_FUN_PARAMETER by error<KtParameter>(PositioningStrategy.VAL_OR_VAR_NODE) {
             parameter<KtKeywordToken>("valOrVar")
         }
-        val VAL_OR_VAR_ON_CATCH_PARAMETER by warning<KtParameter>(PositioningStrategy.VAL_OR_VAR_NODE) {
+        val VAL_OR_VAR_ON_CATCH_PARAMETER by error<KtParameter>(PositioningStrategy.VAL_OR_VAR_NODE) {
             parameter<KtKeywordToken>("valOrVar")
         }
-        val VAL_OR_VAR_ON_SECONDARY_CONSTRUCTOR_PARAMETER by warning<KtParameter>(PositioningStrategy.VAL_OR_VAR_NODE) {
+        val VAL_OR_VAR_ON_SECONDARY_CONSTRUCTOR_PARAMETER by error<KtParameter>(PositioningStrategy.VAL_OR_VAR_NODE) {
             parameter<KtKeywordToken>("valOrVar")
         }
         val INVISIBLE_SETTER by error<PsiElement>(PositioningStrategy.ASSIGNMENT_LHS) {
diff --git a/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt b/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
index 0b0765b3698..63baedf3bf8 100644
--- a/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
+++ b/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
@@ -134,10 +134,10 @@ object FirErrors {
     val FLOAT_LITERAL_OUT_OF_RANGE by error0<PsiElement>()
     val WRONG_LONG_SUFFIX by error0<KtElement>(SourceElementPositioningStrategies.LONG_LITERAL_SUFFIX)
     val DIVISION_BY_ZERO by warning0<KtExpression>()
-    val VAL_OR_VAR_ON_LOOP_PARAMETER by warning1<KtParameter, KtKeywordToken>(SourceElementPositioningStrategies.VAL_OR_VAR_NODE)
-    val VAL_OR_VAR_ON_FUN_PARAMETER by warning1<KtParameter, KtKeywordToken>(SourceElementPositioningStrategies.VAL_OR_VAR_NODE)
-    val VAL_OR_VAR_ON_CATCH_PARAMETER by warning1<KtParameter, KtKeywordToken>(SourceElementPositioningStrategies.VAL_OR_VAR_NODE)
-    val VAL_OR_VAR_ON_SECONDARY_CONSTRUCTOR_PARAMETER by warning1<KtParameter, KtKeywordToken>(SourceElementPositioningStrategies.VAL_OR_VAR_NODE)
+    val VAL_OR_VAR_ON_LOOP_PARAMETER by error1<KtParameter, KtKeywordToken>(SourceElementPositioningStrategies.VAL_OR_VAR_NODE)
+    val VAL_OR_VAR_ON_FUN_PARAMETER by error1<KtParameter, KtKeywordToken>(SourceElementPositioningStrategies.VAL_OR_VAR_NODE)
+    val VAL_OR_VAR_ON_CATCH_PARAMETER by error1<KtParameter, KtKeywordToken>(SourceElementPositioningStrategies.VAL_OR_VAR_NODE)
+    val VAL_OR_VAR_ON_SECONDARY_CONSTRUCTOR_PARAMETER by error1<KtParameter, KtKeywordToken>(SourceElementPositioningStrategies.VAL_OR_VAR_NODE)
     val INVISIBLE_SETTER by error3<PsiElement, FirPropertySymbol, Visibility, CallableId>(SourceElementPositioningStrategies.ASSIGNMENT_LHS)
 
     // Unresolved
diff --git a/compiler/testData/cli/jvm/firError.out b/compiler/testData/cli/jvm/firError.out
index 31a3a294d47..fa215da43fa 100644
--- a/compiler/testData/cli/jvm/firError.out
+++ b/compiler/testData/cli/jvm/firError.out
@@ -1,6 +1,9 @@
 warning: ATTENTION!
  This build uses experimental K2 compiler:
   -Xuse-k2
+compiler/testData/cli/jvm/firError.kt:1:13: error: 'val' on function parameter is not allowed
+fun println(val x: Int) {}
+            ^
 compiler/testData/cli/jvm/firError.kt:5:13: error: variable 'x' must be initialized
     println(x)
             ^