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
@@ -225,12 +225,9 @@
 
     if (MethodDecl && !MethodDecl->isStatic()) {
       QualType ThisPointeeType = MethodDecl->getThisObjectType();
-      // FIXME: Add support for union types.
-      if (!ThisPointeeType->isUnionType()) {
-        ThisPointeeLoc = &createStorageLocation(ThisPointeeType);
-        if (Value *ThisPointeeVal = createValue(ThisPointeeType))
-          setValue(*ThisPointeeLoc, *ThisPointeeVal);
-      }
+      ThisPointeeLoc = &createStorageLocation(ThisPointeeType);
+      if (Value *ThisPointeeVal = createValue(ThisPointeeType))
+        setValue(*ThisPointeeLoc, *ThisPointeeVal);
     }
   }
 }
diff --git a/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp b/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
--- a/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
+++ b/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
@@ -1518,6 +1518,54 @@
       });
 }
 
+TEST(TransferTest, UnionThisMember) {
+  std::string Code = R"(
+    union A {
+      int Foo;
+      double Bar;
+
+      void target() {
+        (void)0; // [[p]]
+      }
+    };
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        ASSERT_THAT(Results.keys(), UnorderedElementsAre("p"));
+        const Environment &Env = getEnvironmentAtAnnotation(Results, "p");
+
+        const auto *ThisLoc = dyn_cast<AggregateStorageLocation>(
+            Env.getThisPointeeStorageLocation());
+        ASSERT_THAT(ThisLoc, NotNull());
+
+        const ValueDecl *FooDecl = findValueDecl(ASTCtx, "Foo");
+        ASSERT_THAT(FooDecl, NotNull());
+
+        const auto *FooLoc =
+            cast<ScalarStorageLocation>(&ThisLoc->getChild(*FooDecl));
+        ASSERT_TRUE(isa_and_nonnull<ScalarStorageLocation>(FooLoc));
+
+        const Value *FooVal = Env.getValue(*FooLoc);
+        // TODO: Initialise values inside unions, then change below to
+        // ASSERT_TRUE.
+        ASSERT_FALSE(isa_and_nonnull<IntegerValue>(FooVal));
+
+        const ValueDecl *BarDecl = findValueDecl(ASTCtx, "Bar");
+        ASSERT_THAT(BarDecl, NotNull());
+
+        const auto *BarLoc =
+            cast<ScalarStorageLocation>(&ThisLoc->getChild(*BarDecl));
+        ASSERT_TRUE(isa_and_nonnull<ScalarStorageLocation>(BarLoc));
+
+        const Value *BarVal = Env.getValue(*BarLoc);
+        // TODO: Initialise values inside unions, then change below to
+        // ASSERT_TRUE.
+        ASSERT_FALSE(isa_and_nonnull<IntegerValue>(BarVal));
+      });
+}
+
 TEST(TransferTest, StructThisInLambda) {
   std::string ThisCaptureCode = R"(
     struct A {