diff --git a/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
--- a/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
@@ -767,7 +767,7 @@
     Nullability RequiredNullability =
         getNullabilityAnnotation(Param->getType());
     Nullability ArgExprTypeLevelNullability =
-        getNullabilityAnnotation(ArgExpr->getType());
+        getNullabilityAnnotation(lookThroughImplicitCasts(ArgExpr)->getType());
 
     unsigned ParamIdx = Param->getFunctionScopeIndex() + 1;
 
diff --git a/clang/test/Analysis/nullability.mm b/clang/test/Analysis/nullability.mm
--- a/clang/test/Analysis/nullability.mm
+++ b/clang/test/Analysis/nullability.mm
@@ -69,6 +69,7 @@
 void takesNonnull(Dummy *_Nonnull);
 void takesUnspecified(Dummy *);
 void takesNonnullBlock(void (^ _Nonnull)(void));
+void takesNonnullObject(TestObject *_Nonnull);
 
 Dummy *_Nullable returnsNullable();
 Dummy *_Nonnull returnsNonnull();
@@ -264,6 +265,11 @@
   return (Dummy * _Nonnull)0;         // no-warning
 }
 
+void testImplicitCastNilToNonnull() {
+  id obj = nil;
+  takesNonnullObject(obj); // expected-warning {{nil passed to a callee that requires a non-null 1st parameter}}
+}
+
 void testIndirectCastNilToNonnullAndPass() {
   Dummy *p = (Dummy * _Nonnull)0;
   // FIXME: Ideally the cast above would suppress this warning.