Index: lib/StaticAnalyzer/Checkers/RetainCountChecker.cpp
===================================================================
--- lib/StaticAnalyzer/Checkers/RetainCountChecker.cpp
+++ lib/StaticAnalyzer/Checkers/RetainCountChecker.cpp
@@ -1722,6 +1722,17 @@
     }
   };
 
+  class BadReleaseByBlock : public CFRefBug {
+  public:
+    BadReleaseByBlock(const CheckerBase *checker)
+        : CFRefBug(checker, "Bad release") {}
+
+    const char *getDescription() const override {
+      return "Incorrect decrement of the reference count of an object that is "
+             "not owned at this point by the current block";
+    }
+  };
+
   class DeallocGC : public CFRefBug {
   public:
     DeallocGC(const CheckerBase *checker)
@@ -2560,7 +2571,8 @@
                     check::RegionChanges,
                     eval::Assume,
                     eval::Call > {
-  mutable std::unique_ptr<CFRefBug> useAfterRelease, releaseNotOwned;
+  mutable std::unique_ptr<CFRefBug> useAfterRelease;
+  mutable std::unique_ptr<CFRefBug> releaseNotOwned, releaseNotOwnedByBlock;
   mutable std::unique_ptr<CFRefBug> deallocGC, deallocNotOwned;
   mutable std::unique_ptr<CFRefBug> overAutorelease, returnNotOwnedForOwned;
   mutable std::unique_ptr<CFRefBug> leakWithinFunction, leakAtReturn;
@@ -3396,9 +3408,15 @@
       BT = useAfterRelease.get();
       break;
     case RefVal::ErrorReleaseNotOwned:
-      if (!releaseNotOwned)
-        releaseNotOwned.reset(new BadRelease(this));
-      BT = releaseNotOwned.get();
+      if (isa<BlockDecl>(C.getLocationContext()->getDecl())) {
+        if (!releaseNotOwnedByBlock)
+          releaseNotOwnedByBlock.reset(new BadReleaseByBlock(this));
+        BT = releaseNotOwnedByBlock.get();
+      } else {
+        if (!releaseNotOwned)
+          releaseNotOwned.reset(new BadRelease(this));
+        BT = releaseNotOwned.get();
+      }
       break;
     case RefVal::ErrorDeallocGC:
       if (!deallocGC)
Index: test/Analysis/retain-release.m
===================================================================
--- test/Analysis/retain-release.m
+++ test/Analysis/retain-release.m
@@ -2300,6 +2300,23 @@
   CFRelease(obj);
 }
 
+//===----------------------------------------------------------------------===//
+// When warning within blocks make it obvious that warnings refer to blocks.
+//===----------------------------------------------------------------------===//
+
+int useBlock(int (^block)());
+void rdar31699502_hardToNoticeBlocks() {
+  if (useBlock(^{
+    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
+    NSArray *array = [NSArray array];
+    [array release]; // expected-warning{{Incorrect decrement of the reference count of an object that is not owned at this point by the current block}}
+    [pool drain];
+    return 0;
+  })) {
+    return;
+  }
+}
+
 // CHECK:  <key>diagnostics</key>
 // CHECK-NEXT:  <array>
 // CHECK-NEXT:   <dict>