diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java b/compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
index 4b287ac09da..ca4c873080f 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
@@ -3714,6 +3714,7 @@ The "returned" value of try expression with no finally is either the last expres
     private StackValue generateExpressionMatch(StackValue expressionToMatch, JetExpression patternExpression) {
         if (expressionToMatch != null) {
             Type subjectType = expressionToMatch.type;
+            markStartLineNumber(patternExpression);
             expressionToMatch.put(subjectType, v);
             JetType condJetType = bindingContext.get(EXPRESSION_TYPE, patternExpression);
             Type condType;
@@ -3738,6 +3739,7 @@ The "returned" value of try expression with no finally is either the last expres
 
     private StackValue generateIsCheck(StackValue expressionToMatch, JetTypeReference typeReference, boolean negated) {
         JetType jetType = bindingContext.get(TYPE, typeReference);
+        markStartLineNumber(typeReference);
         generateInstanceOf(expressionToMatch, jetType, false);
         StackValue value = StackValue.onStack(Type.BOOLEAN_TYPE);
         return negated ? StackValue.not(value) : value;
diff --git a/idea/testData/debugger/tinyApp/outs/whenExpr.out b/idea/testData/debugger/tinyApp/outs/whenExpr.out
new file mode 100644
index 00000000000..81134f02c41
--- /dev/null
+++ b/idea/testData/debugger/tinyApp/outs/whenExpr.out
@@ -0,0 +1,29 @@
+LineBreakpoint created at whenExpr.kt:5
+!JDK_HOME!\bin\java -agentlib:jdwp=transport=dt_socket,address=!HOST_NAME!:!HOST_PORT!,suspend=y,server=n -Dfile.encoding=!FILE_ENCODING! -classpath !APP_PATH!\classes;!KOTLIN_RUNTIME!;!CUSTOM_LIBRARY!;!RT_JAR! whenExpr.WhenExprPackage
+Connected to the target VM, address: '!HOST_NAME!:PORT_NAME!', transport: 'socket'
+whenExpr.kt:5
+whenExpr.kt:6
+whenExpr.kt:7
+whenExpr.kt:10
+whenExpr.kt:14
+whenExpr.kt:17
+whenExpr.kt:19
+whenExpr.kt:20
+whenExpr.kt:21
+whenExpr.kt:24
+whenExpr.kt:28
+whenExpr.kt:31
+whenExpr.kt:33
+whenExpr.kt:34
+whenExpr.kt:35
+whenExpr.kt:38
+whenExpr.kt:39
+whenExpr.kt:45
+whenExpr.kt:47
+whenExpr.kt:48
+whenExpr.kt:49
+whenExpr.kt:50
+whenExpr.kt:59
+Disconnected from the target VM, address: '!HOST_NAME!:PORT_NAME!', transport: 'socket'
+
+Process finished with exit code 0
diff --git a/idea/testData/debugger/tinyApp/src/stepInto/stepInto/whenExpr.kt b/idea/testData/debugger/tinyApp/src/stepInto/stepInto/whenExpr.kt
new file mode 100644
index 00000000000..7682e022656
--- /dev/null
+++ b/idea/testData/debugger/tinyApp/src/stepInto/stepInto/whenExpr.kt
@@ -0,0 +1,62 @@
+package whenExpr
+
+fun main(args: Array<String>) {
+    //Breakpoint!
+    val a: Int? = 0         // 5
+    when (a) {              // 6
+        1 -> {              // 7
+            1 + 1
+        }
+        2 -> {              // 10
+            2 + 1
+        }
+        else -> {
+            0 + 0           // 14
+        }
+    }
+    val b = 1               // 17
+
+    val a1: Number? = 0     // 19
+    when (a1) {             // 20
+        is Float -> {       // 21
+            1 + 1
+        }
+        is Double -> {      // 24
+            2 + 1
+        }
+        else -> {
+            0 + 0           // 28
+        }
+    }
+    val b1 = 1              // 31
+
+    val a2: Int? = 2        // 33
+    when (a2) {             // 34
+        1 -> {              // 35
+            1 + 1
+        }
+        2 -> {              // 38
+            2 + 1           // 39
+        }
+        else -> {
+            0 + 0
+        }
+    }
+    val b2 = 1              // 45
+
+    val a3: Number? = 0f    // 47
+    when (a3) {             // 48
+        is Float -> {       // 49
+            1 + 1           // 50
+        }
+        is Double -> {
+            2 + 1
+        }
+        else -> {
+            0 + 0
+        }
+    }
+    val b3 = 1              // 59
+}
+
+// STEP_INTO: 22
\ No newline at end of file
diff --git a/idea/tests/org/jetbrains/jet/plugin/debugger/KotlinSteppingTestGenerated.java b/idea/tests/org/jetbrains/jet/plugin/debugger/KotlinSteppingTestGenerated.java
index 810878d2d78..c5243c95c54 100644
--- a/idea/tests/org/jetbrains/jet/plugin/debugger/KotlinSteppingTestGenerated.java
+++ b/idea/tests/org/jetbrains/jet/plugin/debugger/KotlinSteppingTestGenerated.java
@@ -224,6 +224,12 @@ public class KotlinSteppingTestGenerated extends AbstractKotlinSteppingTest {
             String fileName = JetTestUtils.navigationMetadata("idea/testData/debugger/tinyApp/src/stepInto/stepInto/forLoop.kt");
             doStepIntoTest(fileName);
         }
+
+        @TestMetadata("whenExpr.kt")
+        public void testWhenExpr() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/debugger/tinyApp/src/stepInto/stepInto/whenExpr.kt");
+            doStepIntoTest(fileName);
+        }
     }
 
     @TestMetadata("idea/testData/debugger/tinyApp/src/filters")