Index: lib/StaticAnalyzer/Core/CallEvent.cpp
===================================================================
--- lib/StaticAnalyzer/Core/CallEvent.cpp
+++ lib/StaticAnalyzer/Core/CallEvent.cpp
@@ -404,6 +404,24 @@
 }
 
 void CXXInstanceCall::getExtraInvalidatedValues(ValueList &Values) const {
+  // Check if this is a call to a const method.
+  if (const CXXMethodDecl *D = cast_or_null<CXXMethodDecl>(getDecl())) {
+    if(D->getCanonicalDecl()->isConst()) {
+      // Check if the containing class/struct has mutable members
+      const MemRegion *ThisRegion = getCXXThisVal().getAsRegion();
+      if (ThisRegion) {
+        MemRegionManager *MemMgr = ThisRegion->getMemRegionManager();
+        const CXXRecordDecl *Parent = D->getParent();
+        for (const auto *I : Parent->fields()) {
+          if (I->isMutable()) {
+            const FieldRegion *FR = MemMgr->getFieldRegion(I, ThisRegion);
+            Values.push_back(loc::MemRegionVal(FR));
+          }
+        }
+      }
+      return;
+    }
+  }
   Values.push_back(getCXXThisVal());
 }
 
Index: test/Analysis/PR21606.cpp
===================================================================
--- test/Analysis/PR21606.cpp
+++ test/Analysis/PR21606.cpp
@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -analyze -analyzer-checker=core
+// PR21606
+
+struct s1 {
+    void g(const int *i) const;
+};
+
+struct s2 {
+    void f(int *i) {
+        m_i = i;
+        m_s.g(m_i);
+        if (m_i)
+            *i = 42; // no-warning
+    }
+
+    int *m_i;
+    s1 m_s;
+};
+
+int main()
+{
+    s2().f(0);
+}
\ No newline at end of file
Index: test/Analysis/method-call.cpp
===================================================================
--- test/Analysis/method-call.cpp
+++ test/Analysis/method-call.cpp
@@ -13,6 +13,17 @@
   int x;
 };
 
+struct C {
+  int x;
+  void foo() const;
+  void bar();
+};
+
+struct D {
+  mutable int x;
+  void foo() const;
+};
+
 void testNullObject(A *a) {
   clang_analyzer_eval(a); // expected-warning{{UNKNOWN}}
   (void)a->getx(); // assume we know what we're doing
@@ -45,3 +56,21 @@
   B t2(t);
   clang_analyzer_eval(t.x == 0); // expected-warning{{TRUE}}
 }
+
+void checkThatConstMethodWithoutDefinitionDoesNotInvalidateObject() {
+  C t;
+  t.x = 3;
+  t.foo();
+  clang_analyzer_eval(t.x == 3); // expected-warning{{TRUE}}
+  // Test non-const does invalidate
+  t.bar();
+  clang_analyzer_eval(t.x); // expected-warning{{UNKNOWN}}
+}
+
+void checkThatConstMethodDoesInvalidateMutableFields() {
+  D t;
+  t.x = 3;
+  t.foo();
+  clang_analyzer_eval(t.x); // expected-warning{{UNKNOWN}}
+}
+