diff --git a/compiler/cli/src/org/jetbrains/kotlin/cli/jvm/jvmArguments.kt b/compiler/cli/src/org/jetbrains/kotlin/cli/jvm/jvmArguments.kt
index 97a7aee5242..60267840fd7 100644
--- a/compiler/cli/src/org/jetbrains/kotlin/cli/jvm/jvmArguments.kt
+++ b/compiler/cli/src/org/jetbrains/kotlin/cli/jvm/jvmArguments.kt
@@ -165,7 +165,12 @@ fun CompilerConfiguration.configureAdvancedJvmOptions(arguments: K2JVMCompilerAr
 
     put(JVMConfigurationKeys.PARAMETERS_METADATA, arguments.javaParameters)
 
-    val useIR = (arguments.useIR && !arguments.useOldBackend) || arguments.useFir
+    val useIR = arguments.useFir ||
+            if (languageVersionSettings.supportsFeature(LanguageFeature.JvmIrEnabledByDefault)) {
+                !arguments.useOldBackend
+            } else {
+                arguments.useIR && !arguments.useOldBackend
+            }
     put(JVMConfigurationKeys.IR, useIR)
 
     val abiStability = JvmAbiStability.fromStringOrNull(arguments.abiStability)
diff --git a/compiler/testData/cli/jvm/jvmIrByDefault.kt b/compiler/testData/cli/jvm/jvmIrByDefault.kt
new file mode 100644
index 00000000000..16576cea591
--- /dev/null
+++ b/compiler/testData/cli/jvm/jvmIrByDefault.kt
@@ -0,0 +1,13 @@
+// This test checks that with -language-version 1.4 we're using the old JVM backend,
+// and with -language-version 1.5 -- the new JVM IR backend.
+// JVM IR doesn't produce classes for local functions, so the test checks which backend
+// is used by asserting that the file for the anonymous class does or doesn't exist.
+
+// Feel free to remove both _1_4 and _1_5 tests as soon as either the old JVM backend
+// or LV 1.4 is removed, whichever happens earlier.
+
+class C {
+    fun test() {
+        fun local() {}
+    }
+}
diff --git a/compiler/testData/cli/jvm/jvmIrByDefault1_4.args b/compiler/testData/cli/jvm/jvmIrByDefault1_4.args
new file mode 100644
index 00000000000..e82803d8640
--- /dev/null
+++ b/compiler/testData/cli/jvm/jvmIrByDefault1_4.args
@@ -0,0 +1,5 @@
+$TESTDATA_DIR$/jvmIrByDefault.kt
+-d
+$TEMP_DIR$
+-language-version
+1.4
diff --git a/compiler/testData/cli/jvm/jvmIrByDefault1_4.out b/compiler/testData/cli/jvm/jvmIrByDefault1_4.out
new file mode 100644
index 00000000000..d86bac9de59
--- /dev/null
+++ b/compiler/testData/cli/jvm/jvmIrByDefault1_4.out
@@ -0,0 +1 @@
+OK
diff --git a/compiler/testData/cli/jvm/jvmIrByDefault1_4.test b/compiler/testData/cli/jvm/jvmIrByDefault1_4.test
new file mode 100644
index 00000000000..6992627b278
--- /dev/null
+++ b/compiler/testData/cli/jvm/jvmIrByDefault1_4.test
@@ -0,0 +1 @@
+// EXISTS: C$test$1.class
diff --git a/compiler/testData/cli/jvm/jvmIrByDefault1_5.args b/compiler/testData/cli/jvm/jvmIrByDefault1_5.args
new file mode 100644
index 00000000000..21fdb80fe66
--- /dev/null
+++ b/compiler/testData/cli/jvm/jvmIrByDefault1_5.args
@@ -0,0 +1,5 @@
+$TESTDATA_DIR$/jvmIrByDefault.kt
+-d
+$TEMP_DIR$
+-language-version
+1.5
diff --git a/compiler/testData/cli/jvm/jvmIrByDefault1_5.out b/compiler/testData/cli/jvm/jvmIrByDefault1_5.out
new file mode 100644
index 00000000000..5be61f3d3c9
--- /dev/null
+++ b/compiler/testData/cli/jvm/jvmIrByDefault1_5.out
@@ -0,0 +1,2 @@
+warning: language version 1.5 is experimental, there are no backwards compatibility guarantees for new language and library features
+OK
diff --git a/compiler/testData/cli/jvm/jvmIrByDefault1_5.test b/compiler/testData/cli/jvm/jvmIrByDefault1_5.test
new file mode 100644
index 00000000000..c7ca4da7275
--- /dev/null
+++ b/compiler/testData/cli/jvm/jvmIrByDefault1_5.test
@@ -0,0 +1 @@
+// ABSENT: C$test$1.class
diff --git a/compiler/tests-gen/org/jetbrains/kotlin/cli/CliTestGenerated.java b/compiler/tests-gen/org/jetbrains/kotlin/cli/CliTestGenerated.java
index 7ae942f9f08..4966fb383e0 100644
--- a/compiler/tests-gen/org/jetbrains/kotlin/cli/CliTestGenerated.java
+++ b/compiler/tests-gen/org/jetbrains/kotlin/cli/CliTestGenerated.java
@@ -541,6 +541,16 @@ public class CliTestGenerated extends AbstractCliTest {
             runTest("compiler/testData/cli/jvm/jvmDefaultAll.args");
         }
 
+        @TestMetadata("jvmIrByDefault1_4.args")
+        public void testJvmIrByDefault1_4() throws Exception {
+            runTest("compiler/testData/cli/jvm/jvmIrByDefault1_4.args");
+        }
+
+        @TestMetadata("jvmIrByDefault1_5.args")
+        public void testJvmIrByDefault1_5() throws Exception {
+            runTest("compiler/testData/cli/jvm/jvmIrByDefault1_5.args");
+        }
+
         @TestMetadata("jvmRecordOk.args")
         public void testJvmRecordOk() throws Exception {
             runTest("compiler/testData/cli/jvm/jvmRecordOk.args");
diff --git a/compiler/util/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt b/compiler/util/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt
index f18abdfe537..0a6ec5932cc 100644
--- a/compiler/util/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt
+++ b/compiler/util/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt
@@ -144,6 +144,7 @@ enum class LanguageFeature(
 
     AllowSealedInheritorsInDifferentFilesOfSamePackage(KOTLIN_1_5),
     SealedInterfaces(KOTLIN_1_5),
+    JvmIrEnabledByDefault(KOTLIN_1_5),
 
     /*
      * Improvements include the following: