diff --git a/clang/lib/StaticAnalyzer/Checkers/IdempotentOperationChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/IdempotentOperationChecker.cpp
index 633648ec6c22..7f64f8e2c40a 100644
--- a/clang/lib/StaticAnalyzer/Checkers/IdempotentOperationChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/IdempotentOperationChecker.cpp
@@ -357,8 +357,15 @@ void IdempotentOperationChecker::PostVisitBinaryOperator(
                                                       const BinaryOperator *B) {
   // Add the ExplodedNode we just visited
   BinaryOperatorData &Data = hash[B];
-  assert(isa<BinaryOperator>(cast<StmtPoint>(C.getPredecessor()
-                                             ->getLocation()).getStmt()));
+
+  const Stmt *predStmt 
+    = cast<StmtPoint>(C.getPredecessor()->getLocation()).getStmt();
+  
+  // Ignore implicit calls to setters.
+  if (isa<ObjCPropertyRefExpr>(predStmt))
+    return;
+  
+  assert(isa<BinaryOperator>(predStmt));
   Data.explodedNodes.Add(C.getPredecessor());
 }
 
diff --git a/clang/test/Analysis/idempotent-operations.m b/clang/test/Analysis/idempotent-operations.m
index 3f68206b168f..bda98fa71713 100644
--- a/clang/test/Analysis/idempotent-operations.m
+++ b/clang/test/Analysis/idempotent-operations.m
@@ -4,10 +4,12 @@ typedef signed char BOOL;
 typedef unsigned long NSUInteger;
 typedef struct _NSZone NSZone;
 @protocol NSObject  - (BOOL)isEqual:(id)object;
-@end    @interface NSObject <NSObject> {
-}
 @end
 
+@interface NSObject {}
+  @property int locked;
+  @property(nonatomic, readonly) NSObject *media;
+@end
 
 // <rdar://problem/8725041> - Don't flag idempotent operation warnings when
 // a method may invalidate an instance variable.
@@ -32,3 +34,9 @@ typedef struct _NSZone NSZone;
 }
 @end
 
+// Test that the idempotent operations checker works in the prescence
+// of property expressions.
+void pr9116(NSObject *placeholder) {
+  int x = placeholder.media.locked = placeholder ? 1 : 0;
+}
+