Index: lib/Index/IndexBody.cpp
===================================================================
--- lib/Index/IndexBody.cpp
+++ lib/Index/IndexBody.cpp
@@ -399,6 +399,19 @@
     return true;
   }
 
+  bool TraverseLambdaExpr(LambdaExpr* LE) {
+    // Clang's default behavior is only visiting the visible parts of lambda
+    // expressions, thus the implicitly (and importantly) generated call
+    // operator is not visited, which results in ignoring parameters of
+    // the lambda expressions.
+    bool Result = RecursiveASTVisitor::TraverseLambdaExpr(LE);
+    // Index parameters of the lambda expressions.
+    if (IndexCtx.shouldIndexFunctionLocalSymbols())
+      for (const auto* PI : LE->getCallOperator()->parameters())
+        IndexCtx.handleDecl(PI);
+    return Result;
+  }
+
   // RecursiveASTVisitor visits both syntactic and semantic forms, duplicating
   // the things that we visit. Make sure to only visit the semantic form.
   // Also visit things that are in the syntactic form but not the semantic one,
Index: test/Index/cxx11-lambdas.cpp
===================================================================
--- test/Index/cxx11-lambdas.cpp
+++ test/Index/cxx11-lambdas.cpp
@@ -31,3 +31,4 @@
 // CHECK-INDEX: [indexEntityReference]: kind: variable | name: localA | USR: c:cxx11-lambdas.cpp@100@S@X@F@f#@localA | lang: C | cursor: DeclRefExpr=localA:6:9 | loc: 8:14
 // CHECK-INDEX: [indexEntityReference]: kind: variable | name: localB | USR: c:cxx11-lambdas.cpp@100@S@X@F@f#@localB | lang: C | cursor: DeclRefExpr=localB:6:17 | loc: 8:23
 // CHECK-INDEX: [indexEntityReference]: kind: variable | name: x | USR: c:cxx11-lambdas.cpp@157@S@X@F@f#@Sa@F@operator()#I#1@x | lang: C | cursor: DeclRefExpr=x:7:46 | loc: 8:32
+// CHECK-INDEX: [indexDeclaration]: kind: variable | name: x | USR: c:cxx11-lambdas.cpp@157@S@X@F@f#@Sa@F@operator()#I#1@x | lang: C | cursor: ParmDecl=x:7:46 (Definition) | loc: 7:46
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