diff --git a/sandboxed_api/BUILD.bazel b/sandboxed_api/BUILD.bazel
index 63f4ef3..0a6fa5d 100644
--- a/sandboxed_api/BUILD.bazel
+++ b/sandboxed_api/BUILD.bazel
@@ -86,6 +86,7 @@ cc_library(
         "//sandboxed_api/util:status",
         "@com_google_absl//absl/base",
         "@com_google_absl//absl/base:core_headers",
+        "@com_google_absl//absl/base:dynamic_annotations",
         "@com_google_absl//absl/container:flat_hash_map",
         "@com_google_absl//absl/memory",
         "@com_google_absl//absl/status",
diff --git a/sandboxed_api/CMakeLists.txt b/sandboxed_api/CMakeLists.txt
index a023d86..220aae8 100644
--- a/sandboxed_api/CMakeLists.txt
+++ b/sandboxed_api/CMakeLists.txt
@@ -75,7 +75,8 @@ add_library(sapi_sapi ${SAPI_LIB_TYPE}
 )
 add_library(sapi::sapi ALIAS sapi_sapi)
 target_link_libraries(sapi_sapi
-  PRIVATE absl::flat_hash_map
+  PRIVATE absl::dynamic_annotations
+          absl::flat_hash_map
           absl::memory
           absl::status
           absl::statusor
diff --git a/sandboxed_api/client.cc b/sandboxed_api/client.cc
index ab8c5ec..320e053 100644
--- a/sandboxed_api/client.cc
+++ b/sandboxed_api/client.cc
@@ -396,6 +396,8 @@ void ServeRequest(sandbox2::Comms* comms) {
   }
 
   if (ret.ret_type == v::Type::kFloat) {
+    // Make MSAN happy with long double.
+    ABSL_ANNOTATE_MEMORY_IS_INITIALIZED(&ret.float_val, sizeof(ret.float_val));
     VLOG(1) << "Returned value: " << ret.float_val
             << ", Success: " << (ret.success ? "Yes" : "No");
   } else {
diff --git a/sandboxed_api/sandbox.cc b/sandboxed_api/sandbox.cc
index 3f51f4c..08fd07a 100644
--- a/sandboxed_api/sandbox.cc
+++ b/sandboxed_api/sandbox.cc
@@ -24,6 +24,7 @@
 
 #include <glog/logging.h>
 #include "absl/base/casts.h"
+#include "absl/base/dynamic_annotations.h"
 #include "absl/base/macros.h"
 #include "absl/memory/memory.h"
 #include "absl/status/status.h"
@@ -323,6 +324,9 @@ absl::Status Sandbox::Call(const std::string& func, v::Callable* ret,
     if (arg->GetType() == v::Type::kFloat) {
       arg->GetDataFromPtr(&rfcall.args[i].arg_float,
                           sizeof(rfcall.args[0].arg_float));
+      // Make MSAN happy with long double.
+      ABSL_ANNOTATE_MEMORY_IS_INITIALIZED(&rfcall.args[i].arg_float,
+                                          sizeof(rfcall.args[0].arg_float));
     } else {
       arg->GetDataFromPtr(&rfcall.args[i].arg_int,
                           sizeof(rfcall.args[0].arg_int));
diff --git a/sandboxed_api/var_reg.h b/sandboxed_api/var_reg.h
index bc46e6f..3cf3661 100644
--- a/sandboxed_api/var_reg.h
+++ b/sandboxed_api/var_reg.h
@@ -57,9 +57,7 @@ class Reg : public Callable {
                 "Only register-sized types are allowed as template argument "
                 "for class Reg.");
 
-  Reg() : Reg(static_cast<T>(0)) {}
-
-  explicit Reg(const T val) {
+  explicit Reg(const T val = {}) {
     val_ = val;
     SetLocal(&val_);
   }