Index: lib/Analysis/BodyFarm.cpp
===================================================================
--- lib/Analysis/BodyFarm.cpp
+++ lib/Analysis/BodyFarm.cpp
@@ -807,6 +807,11 @@
 
   D = D->getCanonicalDecl();
 
+  // We should not try to synthesize explicitly redefined accessors.
+  // We do not know for sure how they behave.
+  if (!D->isImplicit())
+    return nullptr;
+
   Optional<Stmt *> &Val = Bodies[D];
   if (Val.hasValue())
     return Val.getValue();
Index: test/Analysis/properties.m
===================================================================
--- test/Analysis/properties.m
+++ test/Analysis/properties.m
@@ -1005,3 +1005,38 @@
 
 #endif // non-ARC
 
+@interface ExplicitAccessorInCategory : NSObject
+@property(readonly) int normal;
+- (int)normal;
+@property(readonly) int no_custom_accessor;
+@end
+
+@interface ExplicitAccessorInCategory ()
+@property(readonly) int in_category;
+
+@property(readonly) int still_no_custom_accessor;
+// This is an ordinary method, not a getter.
+- (int)still_no_custom_accessor;
+@end
+
+@interface ExplicitAccessorInCategory ()
+- (int)in_category;
+
+// This is an ordinary method, not a getter.
+- (int)no_custom_accessor;
+@end
+
+@implementation ExplicitAccessorInCategory
+- (void)foo {
+	// Make sure we don't farm bodies for explicit accessors: in particular,
+	// we're not sure that the accessor always returns the same value.
+	clang_analyzer_eval(self.normal == self.normal); // expected-warning{{UNKNOWN}}
+	// Also this used to crash.
+	clang_analyzer_eval(self.in_category == self.in_category); // expected-warning{{UNKNOWN}}
+
+	// When there is no explicit accessor defined (even if it looks like there is),
+	// farm the getter body and see if it does actually always yield the same value.
+	clang_analyzer_eval(self.no_custom_accessor == self.no_custom_accessor); // expected-warning{{TRUE}}
+	clang_analyzer_eval(self.still_no_custom_accessor == self.still_no_custom_accessor); // expected-warning{{TRUE}}
+}
+@end