diff --git a/clang/lib/StaticAnalyzer/Frontend/AnalysisConsumer.cpp b/clang/lib/StaticAnalyzer/Frontend/AnalysisConsumer.cpp
--- a/clang/lib/StaticAnalyzer/Frontend/AnalysisConsumer.cpp
+++ b/clang/lib/StaticAnalyzer/Frontend/AnalysisConsumer.cpp
@@ -408,6 +408,12 @@
   //   Count naming convention errors more aggressively.
   if (isa<ObjCMethodDecl>(D))
     return false;
+
+  // If a function with a _Nullable parameter has at least one caller, the
+  // checker behaves as though no other parameter value is possible. This is
+  // because the static analyzer doesn't re-analyse functions as top level.
+  return false;
+
   // We also want to reanalyze all C++ copy and move assignment operators to
   // separately check the two cases where 'this' aliases with the parameter and
   // where it may not. (cplusplus.SelfAssignmentChecker)