diff --git a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
--- a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
+++ b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
@@ -93,7 +93,18 @@
                                   Environment::ValueModel &Model) {
   // Join distinct boolean values preserving information about the constraints
   // in the respective path conditions.
-  if (auto *Expr1 = dyn_cast<BoolValue>(&Val1)) {
+  if (Type->isBooleanType()) {
+    // FIXME: This is sort of workaround. Since now we just ignore all (implicit)
+    // integral casts, treating the resulting value as the same as the underlying
+    // value, it could cause inconsistency between values after `Join` if in
+    // some paths the type doesn't strictly match:
+    //
+    // std::optional<bool> o;
+    // int x;
+    // if (o.has_value()) {
+    //   x = o.value();
+    // }
+    auto *Expr1 = cast<BoolValue>(&Val1);
     auto *Expr2 = cast<BoolValue>(&Val2);
     auto &MergedVal = MergedEnv.makeAtomicBoolValue();
     MergedEnv.addToFlowCondition(MergedEnv.makeOr(
diff --git a/clang/unittests/Analysis/FlowSensitive/UncheckedOptionalAccessModelTest.cpp b/clang/unittests/Analysis/FlowSensitive/UncheckedOptionalAccessModelTest.cpp
--- a/clang/unittests/Analysis/FlowSensitive/UncheckedOptionalAccessModelTest.cpp
+++ b/clang/unittests/Analysis/FlowSensitive/UncheckedOptionalAccessModelTest.cpp
@@ -2970,6 +2970,23 @@
       cxxConstructorDecl(ofClass(hasName("Target"))));
 }
 
+// This is regression test, it shouldn't crash.
+TEST_P(UncheckedOptionalAccessTest, Bitfield) {
+  using namespace ast_matchers;
+  ExpectDiagnosticsFor(
+      R"(
+    #include "unchecked_optional_access_test.h"
+    struct Dst {
+      unsigned int n : 1;
+    };
+    void target() {
+      $ns::$optional<bool> v;
+      Dst d;
+      if (v.has_value())
+        d.n = v.value();
+    }
+  )");
+}
 // FIXME: Add support for:
 // - constructors (copy, move)
 // - assignment operators (default, copy, move)