diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/parsing/JetExpressionParsing.java b/compiler/frontend/src/org/jetbrains/jet/lang/parsing/JetExpressionParsing.java
index 26217d9ec9f..cf8e51c37e8 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/parsing/JetExpressionParsing.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/parsing/JetExpressionParsing.java
@@ -670,7 +670,7 @@ public class JetExpressionParsing extends AbstractJetParsing {
 
     /*
      * when
-     *   : "when" "(" (modifiers "val" SimpleName "=")? element ")" "{"
+     *   : "when" ("(" (modifiers "val" SimpleName "=")? element ")")? "{"
      *         whenEntry*
      *     "}"
      *   ;
@@ -682,22 +682,26 @@ public class JetExpressionParsing extends AbstractJetParsing {
 
         advance(); // WHEN_KEYWORD
 
+        // Parse condition
         myBuilder.disableNewlines();
-        expect(LPAR, "Expecting '('");
+        if (at(LPAR)) {
+            advanceAt(LPAR);
 
-        int valPos = matchTokenStreamPredicate(new FirstBefore(new At(VAL_KEYWORD), new AtSet(RPAR, LBRACE, RBRACE, SEMICOLON, EQ)));
-        if (valPos >= 0) {
-            PsiBuilder.Marker property = mark();
-            myJetParsing.parseModifierList(MODIFIER_LIST, true);
-            myJetParsing.parseProperty(true);
-            property.done(PROPERTY);
-        } else {
-            parseExpression();
+            int valPos = matchTokenStreamPredicate(new FirstBefore(new At(VAL_KEYWORD), new AtSet(RPAR, LBRACE, RBRACE, SEMICOLON, EQ)));
+            if (valPos >= 0) {
+                PsiBuilder.Marker property = mark();
+                myJetParsing.parseModifierList(MODIFIER_LIST, true);
+                myJetParsing.parseProperty(true);
+                property.done(PROPERTY);
+            } else {
+                parseExpression();
+            }
+
+            expect(RPAR, "Expecting ')'");
         }
-
-        expect(RPAR, "Expecting ')'");
         myBuilder.restoreNewlinesState();
 
+        // Parse when block
         myBuilder.enableNewlines();
         expect(LBRACE, "Expecting '{'");
 
diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/psi/JetWhenExpression.java b/compiler/frontend/src/org/jetbrains/jet/lang/psi/JetWhenExpression.java
index 97c736e507c..bbec3d4075c 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/psi/JetWhenExpression.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/psi/JetWhenExpression.java
@@ -20,7 +20,7 @@ public class JetWhenExpression extends JetExpression {
         return findChildrenByType(JetNodeTypes.WHEN_ENTRY);
     }
 
-    @Nullable @IfNotParsed
+    @Nullable
     public JetExpression getSubjectExpression() {
         return findChildByClass(JetExpression.class);
     }
diff --git a/compiler/testData/psi/When.jet b/compiler/testData/psi/When.jet
index a169a11155c..48f1055329c 100644
--- a/compiler/testData/psi/When.jet
+++ b/compiler/testData/psi/When.jet
@@ -70,3 +70,14 @@ fun foo() {
     is a.a @ (val b, b) => c
   }
 }
+
+fun whenWithoutCondition(i : Int) {
+  val j = 12
+  when {
+    3 => -1
+    i == 3 => -1
+    j < i, j == i => -1
+    i is Int => 1
+    else => 2
+  }
+}
diff --git a/compiler/testData/psi/When.txt b/compiler/testData/psi/When.txt
index 110bad28a3f..7abeb1afcb3 100644
--- a/compiler/testData/psi/When.txt
+++ b/compiler/testData/psi/When.txt
@@ -1205,4 +1205,141 @@ JetFile: When.jet
           PsiWhiteSpace('\n  ')
           PsiElement(RBRACE)('}')
         PsiWhiteSpace('\n')
+        PsiElement(RBRACE)('}')
+    PsiWhiteSpace('\n\n')
+    FUN
+      PsiElement(fun)('fun')
+      PsiWhiteSpace(' ')
+      PsiElement(IDENTIFIER)('whenWithoutCondition')
+      VALUE_PARAMETER_LIST
+        PsiElement(LPAR)('(')
+        VALUE_PARAMETER
+          PsiElement(IDENTIFIER)('i')
+          PsiWhiteSpace(' ')
+          PsiElement(COLON)(':')
+          PsiWhiteSpace(' ')
+          TYPE_REFERENCE
+            USER_TYPE
+              REFERENCE_EXPRESSION
+                PsiElement(IDENTIFIER)('Int')
+        PsiElement(RPAR)(')')
+      PsiWhiteSpace(' ')
+      BLOCK
+        PsiElement(LBRACE)('{')
+        PsiWhiteSpace('\n  ')
+        PROPERTY
+          PsiElement(val)('val')
+          PsiWhiteSpace(' ')
+          PsiElement(IDENTIFIER)('j')
+          PsiWhiteSpace(' ')
+          PsiElement(EQ)('=')
+          PsiWhiteSpace(' ')
+          INTEGER_CONSTANT
+            PsiElement(INTEGER_LITERAL)('12')
+        PsiWhiteSpace('\n  ')
+        WHEN
+          PsiElement(when)('when')
+          PsiWhiteSpace(' ')
+          PsiElement(LBRACE)('{')
+          PsiWhiteSpace('\n    ')
+          WHEN_ENTRY
+            WHEN_CONDITION_IS_PATTERN
+              EXPRESSION_PATTERN
+                INTEGER_CONSTANT
+                  PsiElement(INTEGER_LITERAL)('3')
+            PsiWhiteSpace(' ')
+            PsiElement(DOUBLE_ARROW)('=>')
+            PsiWhiteSpace(' ')
+            PREFIX_EXPRESSION
+              OPERATION_REFERENCE
+                PsiElement(MINUS)('-')
+              INTEGER_CONSTANT
+                PsiElement(INTEGER_LITERAL)('1')
+          PsiWhiteSpace('\n    ')
+          WHEN_ENTRY
+            WHEN_CONDITION_IS_PATTERN
+              EXPRESSION_PATTERN
+                BINARY_EXPRESSION
+                  REFERENCE_EXPRESSION
+                    PsiElement(IDENTIFIER)('i')
+                  PsiWhiteSpace(' ')
+                  OPERATION_REFERENCE
+                    PsiElement(EQEQ)('==')
+                  PsiWhiteSpace(' ')
+                  INTEGER_CONSTANT
+                    PsiElement(INTEGER_LITERAL)('3')
+            PsiWhiteSpace(' ')
+            PsiElement(DOUBLE_ARROW)('=>')
+            PsiWhiteSpace(' ')
+            PREFIX_EXPRESSION
+              OPERATION_REFERENCE
+                PsiElement(MINUS)('-')
+              INTEGER_CONSTANT
+                PsiElement(INTEGER_LITERAL)('1')
+          PsiWhiteSpace('\n    ')
+          WHEN_ENTRY
+            WHEN_CONDITION_IS_PATTERN
+              EXPRESSION_PATTERN
+                BINARY_EXPRESSION
+                  REFERENCE_EXPRESSION
+                    PsiElement(IDENTIFIER)('j')
+                  PsiWhiteSpace(' ')
+                  OPERATION_REFERENCE
+                    PsiElement(LT)('<')
+                  PsiWhiteSpace(' ')
+                  REFERENCE_EXPRESSION
+                    PsiElement(IDENTIFIER)('i')
+            PsiElement(COMMA)(',')
+            PsiWhiteSpace(' ')
+            WHEN_CONDITION_IS_PATTERN
+              EXPRESSION_PATTERN
+                BINARY_EXPRESSION
+                  REFERENCE_EXPRESSION
+                    PsiElement(IDENTIFIER)('j')
+                  PsiWhiteSpace(' ')
+                  OPERATION_REFERENCE
+                    PsiElement(EQEQ)('==')
+                  PsiWhiteSpace(' ')
+                  REFERENCE_EXPRESSION
+                    PsiElement(IDENTIFIER)('i')
+            PsiWhiteSpace(' ')
+            PsiElement(DOUBLE_ARROW)('=>')
+            PsiWhiteSpace(' ')
+            PREFIX_EXPRESSION
+              OPERATION_REFERENCE
+                PsiElement(MINUS)('-')
+              INTEGER_CONSTANT
+                PsiElement(INTEGER_LITERAL)('1')
+          PsiWhiteSpace('\n    ')
+          WHEN_ENTRY
+            WHEN_CONDITION_IS_PATTERN
+              EXPRESSION_PATTERN
+                BINARY_WITH_PATTERN
+                  REFERENCE_EXPRESSION
+                    PsiElement(IDENTIFIER)('i')
+                  PsiWhiteSpace(' ')
+                  OPERATION_REFERENCE
+                    PsiElement(is)('is')
+                  PsiWhiteSpace(' ')
+                  TYPE_PATTERN
+                    TYPE_REFERENCE
+                      USER_TYPE
+                        REFERENCE_EXPRESSION
+                          PsiElement(IDENTIFIER)('Int')
+            PsiWhiteSpace(' ')
+            PsiElement(DOUBLE_ARROW)('=>')
+            PsiWhiteSpace(' ')
+            INTEGER_CONSTANT
+              PsiElement(INTEGER_LITERAL)('1')
+          PsiWhiteSpace('\n    ')
+          WHEN_ENTRY
+            PsiElement(else)('else')
+            PsiWhiteSpace(' ')
+            PsiElement(DOUBLE_ARROW)('=>')
+            PsiWhiteSpace(' ')
+            INTEGER_CONSTANT
+              PsiElement(INTEGER_LITERAL)('2')
+          PsiWhiteSpace('\n  ')
+          PsiElement(RBRACE)('}')
+        PsiWhiteSpace('\n')
         PsiElement(RBRACE)('}')
\ No newline at end of file
diff --git a/grammar/src/when.grm b/grammar/src/when.grm
index 4b0dd363a83..864f1602161 100644
--- a/grammar/src/when.grm
+++ b/grammar/src/when.grm
@@ -5,7 +5,7 @@ bq. See [Pattern matching]
 */
 
 when
-  : "when" "(" (modifiers "val" SimpleName "=")? expression ")" "{"
+  : "when" ("(" (modifiers "val" SimpleName "=")? expression ")")? "{"
         whenEntry*
     "}"
   ;