diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/AsmUtil.java b/compiler/backend/src/org/jetbrains/jet/codegen/AsmUtil.java
index 60aa5cc8554..8e2418b9070 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/AsmUtil.java
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/AsmUtil.java
@@ -52,6 +52,7 @@ import java.util.Set;
 import static org.jetbrains.jet.codegen.JvmCodegenUtil.*;
 import static org.jetbrains.jet.lang.resolve.DescriptorUtils.*;
 import static org.jetbrains.jet.lang.resolve.java.AsmTypeConstants.JAVA_STRING_TYPE;
+import static org.jetbrains.jet.lang.resolve.java.AsmTypeConstants.getType;
 import static org.jetbrains.jet.lang.resolve.java.JvmAnnotationNames.ABI_VERSION_FIELD_NAME;
 import static org.jetbrains.jet.lang.resolve.java.JvmAnnotationNames.KotlinSyntheticClass;
 import static org.jetbrains.jet.lang.resolve.java.mapping.PrimitiveTypesUtil.asmTypeForPrimitive;
@@ -68,6 +69,13 @@ public class AsmUtil {
             KotlinBuiltIns.getInstance().getChar()
     );
 
+    private static final Set<Type> STRING_BUILDER_OBJECT_APPEND_ARG_TYPES = Sets.newHashSet(
+            getType(String.class),
+            getType(StringBuilder.class),
+            getType(StringBuffer.class),
+            getType(CharSequence.class)
+    );
+
     private static final int NO_FLAG_LOCAL = 0;
     public static final int NO_FLAG_PACKAGE_PRIVATE = 0;
 
@@ -308,11 +316,25 @@ public class AsmUtil {
         return type;
     }
 
-    private static Type stringValueOfOrStringBuilderAppendType(Type type) {
+    private static Type stringValueOfType(Type type) {
         int sort = type.getSort();
         return sort == Type.OBJECT || sort == Type.ARRAY
-                   ? AsmTypeConstants.OBJECT_TYPE
-                   : sort == Type.BYTE || sort == Type.SHORT ? Type.INT_TYPE : type;
+               ? AsmTypeConstants.OBJECT_TYPE
+               : sort == Type.BYTE || sort == Type.SHORT ? Type.INT_TYPE : type;
+    }
+
+    private static Type stringBuilderAppendType(Type type) {
+        switch (type.getSort()) {
+            case Type.OBJECT:
+                return STRING_BUILDER_OBJECT_APPEND_ARG_TYPES.contains(type) ? type : AsmTypeConstants.OBJECT_TYPE;
+            case Type.ARRAY:
+                return AsmTypeConstants.OBJECT_TYPE;
+            case Type.BYTE:
+            case Type.SHORT:
+                return Type.INT_TYPE;
+            default:
+                return type;
+        }
     }
 
     public static void genThrow(@NotNull MethodVisitor mv, @NotNull String exception, @NotNull String message) {
@@ -374,12 +396,12 @@ public class AsmUtil {
     }
 
     public static void genInvokeAppendMethod(InstructionAdapter v, Type type) {
-        type = stringValueOfOrStringBuilderAppendType(type);
+        type = stringBuilderAppendType(type);
         v.invokevirtual("java/lang/StringBuilder", "append", "(" + type.getDescriptor() + ")Ljava/lang/StringBuilder;");
     }
 
     public static StackValue genToString(InstructionAdapter v, StackValue receiver, Type receiverType) {
-        Type type = stringValueOfOrStringBuilderAppendType(receiverType);
+        Type type = stringValueOfType(receiverType);
         receiver.put(type, v);
         v.invokestatic("java/lang/String", "valueOf", "(" + type.getDescriptor() + ")Ljava/lang/String;");
         return StackValue.onStack(JAVA_STRING_TYPE);
diff --git a/compiler/testData/codegen/bytecodeText/kt5016.kt b/compiler/testData/codegen/bytecodeText/kt5016.kt
new file mode 100644
index 00000000000..d8d795e8be1
--- /dev/null
+++ b/compiler/testData/codegen/bytecodeText/kt5016.kt
@@ -0,0 +1,10 @@
+// KT-5016 wrong StringBuilder append method invoked
+class kt5016 {
+    fun f1(name : String) : String {
+         return "Hello $name!"
+    }
+}
+
+// 0 INVOKEVIRTUAL java/lang/StringBuilder.append \(Ljava/lang/Object;\)Ljava/lang/StringBuilder
+// 3 INVOKEVIRTUAL java/lang/StringBuilder.append \(Ljava/lang/String;\)Ljava/lang/StringBuilder
+// 1 INVOKEVIRTUAL java/lang/StringBuilder.toString
diff --git a/compiler/testData/codegen/bytecodeText/kt5016int.kt b/compiler/testData/codegen/bytecodeText/kt5016int.kt
new file mode 100644
index 00000000000..62727ef5e67
--- /dev/null
+++ b/compiler/testData/codegen/bytecodeText/kt5016int.kt
@@ -0,0 +1,11 @@
+// KT-5016 wrong StringBuilder append method invoked
+class kt5016int {
+    fun f1(num : Int) : String {
+         return "Hello to all the $num!"
+    }
+}
+
+// 0 INVOKEVIRTUAL java/lang/StringBuilder.append \(Ljava/lang/Object;\)Ljava/lang/StringBuilder
+// 2 INVOKEVIRTUAL java/lang/StringBuilder.append \(Ljava/lang/String;\)Ljava/lang/StringBuilder
+// 1 INVOKEVIRTUAL java/lang/StringBuilder.append \(I\)Ljava/lang/StringBuilder
+// 1 INVOKEVIRTUAL java/lang/StringBuilder.toString
diff --git a/compiler/testData/codegen/bytecodeText/kt5016intOrNull.kt b/compiler/testData/codegen/bytecodeText/kt5016intOrNull.kt
new file mode 100644
index 00000000000..fcd1efb4178
--- /dev/null
+++ b/compiler/testData/codegen/bytecodeText/kt5016intOrNull.kt
@@ -0,0 +1,10 @@
+// KT-5016 wrong StringBuilder append method invoked
+class kt5016intOrNull {
+    fun f1(num : Int?) : String {
+         return "Hello to all the $num!"
+    }
+}
+
+// 1 INVOKEVIRTUAL java/lang/StringBuilder.append \(Ljava/lang/Object;\)Ljava/lang/StringBuilder
+// 2 INVOKEVIRTUAL java/lang/StringBuilder.append \(Ljava/lang/String;\)Ljava/lang/StringBuilder
+// 1 INVOKEVIRTUAL java/lang/StringBuilder.toString
diff --git a/compiler/tests/org/jetbrains/jet/codegen/BytecodeTextTestGenerated.java b/compiler/tests/org/jetbrains/jet/codegen/BytecodeTextTestGenerated.java
index a84f13e8581..db6294f8939 100644
--- a/compiler/tests/org/jetbrains/jet/codegen/BytecodeTextTestGenerated.java
+++ b/compiler/tests/org/jetbrains/jet/codegen/BytecodeTextTestGenerated.java
@@ -107,6 +107,21 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
         doTest("compiler/testData/codegen/bytecodeText/kt2887.kt");
     }
     
+    @TestMetadata("kt5016.kt")
+    public void testKt5016() throws Exception {
+        doTest("compiler/testData/codegen/bytecodeText/kt5016.kt");
+    }
+
+    @TestMetadata("kt5016int.kt")
+    public void testKt5016int() throws Exception {
+        doTest("compiler/testData/codegen/bytecodeText/kt5016int.kt");
+    }
+
+    @TestMetadata("kt5016intOrNull.kt")
+    public void testKt5016intOrNull() throws Exception {
+        doTest("compiler/testData/codegen/bytecodeText/kt5016intOrNull.kt");
+    }
+
     @TestMetadata("noVolatileAnnotation.kt")
     public void testNoVolatileAnnotation() throws Exception {
         doTest("compiler/testData/codegen/bytecodeText/noVolatileAnnotation.kt");