diff --git a/plugins/kotlin/idea/src/org/jetbrains/kotlin/idea/inspections/ReplaceWithStringBuilderAppendRangeInspection.kt b/plugins/kotlin/idea/src/org/jetbrains/kotlin/idea/inspections/ReplaceWithStringBuilderAppendRangeInspection.kt
index a744e57cb147..c81c62e30629 100644
--- a/plugins/kotlin/idea/src/org/jetbrains/kotlin/idea/inspections/ReplaceWithStringBuilderAppendRangeInspection.kt
+++ b/plugins/kotlin/idea/src/org/jetbrains/kotlin/idea/inspections/ReplaceWithStringBuilderAppendRangeInspection.kt
@@ -12,10 +12,12 @@ import org.jetbrains.kotlin.idea.base.resources.KotlinBundle
 import org.jetbrains.kotlin.idea.caches.resolve.resolveToCall
 import org.jetbrains.kotlin.idea.codeinsight.api.classic.inspections.AbstractKotlinInspection
 import org.jetbrains.kotlin.idea.refactoring.fqName.fqName
+import org.jetbrains.kotlin.idea.util.getDataFlowAwareTypes
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.platform.jvm.isJvm
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
+import org.jetbrains.kotlin.types.isNullable
 import org.jetbrains.kotlin.types.typeUtil.isInt
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
@@ -61,6 +63,7 @@ class ReplaceWithStringBuilderAppendRangeInspection : AbstractKotlinInspection()
             val callExpression = calleeExpression.parent as? KtCallExpression ?: return
 
             val args = callExpression.valueArguments
+            val firstArg = args.getOrNull(0)?.getArgumentExpression() ?: return
             val secondArg = args.getOrNull(1)?.getArgumentExpression() ?: return
             val thirdArg = args.getOrNull(2)?.getArgumentExpression() ?: return
 
@@ -74,11 +77,19 @@ class ReplaceWithStringBuilderAppendRangeInspection : AbstractKotlinInspection()
             } else if (secondArgAsInt != 0) {
                 thirdArg.replace(psiFactory.createExpressionByPattern("$0 + $1", secondArg, thirdArg))
             }
+
+            if (firstArg.isNullable()) {
+                firstArg.replace(psiFactory.createExpressionByPattern("$0!!", firstArg))
+            }
         }
 
         private fun KtPsiFactory.createCalleeExpression(functionName: String): KtExpression =
             (createExpression("$functionName()") as KtCallExpression).calleeExpression!!
 
         private fun KtExpression.toIntOrNull(): Int? = safeAs<KtConstantExpression>()?.text?.toIntOrNull()
+
+        private fun KtExpression.isNullable(): Boolean {
+            return getDataFlowAwareTypes(this).any { it.isNullable() }
+        }
     }
 }
diff --git a/plugins/kotlin/idea/tests/test/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java b/plugins/kotlin/idea/tests/test/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java
index 0589afe5f546..bdc1a6fdf8a7 100644
--- a/plugins/kotlin/idea/tests/test/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java
+++ b/plugins/kotlin/idea/tests/test/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java
@@ -13294,6 +13294,16 @@ public abstract class LocalInspectionTestGenerated extends AbstractLocalInspecti
             runTest("testData/inspectionsLocal/replaceWithStringBuilderAppendRange/hasReceiver.kt");
         }
 
+        @TestMetadata("nullableCharArray.kt")
+        public void testNullableCharArray() throws Exception {
+            runTest("testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray.kt");
+        }
+
+        @TestMetadata("nullableCharArray2.kt")
+        public void testNullableCharArray2() throws Exception {
+            runTest("testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray2.kt");
+        }
+
         @TestMetadata("precedence.kt")
         public void testPrecedence() throws Exception {
             runTest("testData/inspectionsLocal/replaceWithStringBuilderAppendRange/precedence.kt");
diff --git a/plugins/kotlin/idea/tests/testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray.kt b/plugins/kotlin/idea/tests/testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray.kt
new file mode 100644
index 000000000000..565f5de21ad0
--- /dev/null
+++ b/plugins/kotlin/idea/tests/testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray.kt
@@ -0,0 +1,6 @@
+// WITH_STDLIB
+fun test(charArray: CharArray?, len: Int): String {
+    return buildString {
+        <caret>append(charArray, 0, len)
+    }
+}
\ No newline at end of file
diff --git a/plugins/kotlin/idea/tests/testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray.kt.after b/plugins/kotlin/idea/tests/testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray.kt.after
new file mode 100644
index 000000000000..856cced1f69a
--- /dev/null
+++ b/plugins/kotlin/idea/tests/testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray.kt.after
@@ -0,0 +1,6 @@
+// WITH_STDLIB
+fun test(charArray: CharArray?, len: Int): String {
+    return buildString {
+        appendRange(charArray!!, 0, len)
+    }
+}
\ No newline at end of file
diff --git a/plugins/kotlin/idea/tests/testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray2.kt b/plugins/kotlin/idea/tests/testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray2.kt
new file mode 100644
index 000000000000..a642462555f4
--- /dev/null
+++ b/plugins/kotlin/idea/tests/testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray2.kt
@@ -0,0 +1,8 @@
+// WITH_STDLIB
+fun test(charArray: CharArray?, len: Int): String {
+    return buildString {
+        if (charArray != null) {
+            <caret>append(charArray, 0, len)
+        }
+    }
+}
\ No newline at end of file
diff --git a/plugins/kotlin/idea/tests/testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray2.kt.after b/plugins/kotlin/idea/tests/testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray2.kt.after
new file mode 100644
index 000000000000..161c8a5b29e3
--- /dev/null
+++ b/plugins/kotlin/idea/tests/testData/inspectionsLocal/replaceWithStringBuilderAppendRange/nullableCharArray2.kt.after
@@ -0,0 +1,8 @@
+// WITH_STDLIB
+fun test(charArray: CharArray?, len: Int): String {
+    return buildString {
+        if (charArray != null) {
+            appendRange(charArray, 0, len)
+        }
+    }
+}
\ No newline at end of file