diff --git a/fml/BUILD.gn b/fml/BUILD.gn
index ef0e996daea6d..04ce5527fef7d 100644
--- a/fml/BUILD.gn
+++ b/fml/BUILD.gn
@@ -202,6 +202,11 @@ source_set("fml") {
       "platform/win/paths_win.cc",
       "platform/win/wstring_conversion.h",
     ]
+
+    if (is_win) {
+      # For wstring_conversion. See issue #50053.
+      defines = [ "_SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING" ]
+    }
   } else {
     sources += [
       "platform/posix/file_posix.cc",
diff --git a/shell/platform/common/cpp/BUILD.gn b/shell/platform/common/cpp/BUILD.gn
index 4646e5c68c9ca..b4d5b0a5bf88b 100644
--- a/shell/platform/common/cpp/BUILD.gn
+++ b/shell/platform/common/cpp/BUILD.gn
@@ -53,6 +53,11 @@ source_set("common_cpp") {
   # won't have a JSON dependency.
   defines = [ "USE_RAPID_JSON" ]
   deps += [ "//third_party/rapidjson" ]
+
+  if (is_win) {
+    # For wstring_conversion. See issue #50053.
+    defines += [ "_SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING" ]
+  }
 }
 
 copy("publish_headers") {
diff --git a/third_party/txt/BUILD.gn b/third_party/txt/BUILD.gn
index 63bf09e444457..e3f07f558736e 100644
--- a/third_party/txt/BUILD.gn
+++ b/third_party/txt/BUILD.gn
@@ -28,6 +28,14 @@ config("txt_config") {
   include_dirs = [ "src" ]
 }
 
+config("allow_posix_names") {
+  if (is_win && is_clang) {
+    # POSIX names of many functions are marked deprecated by default;
+    # disable that since they are used for cross-platform compatibility.
+    defines = [ "_CRT_NONSTDC_NO_DEPRECATE" ]
+  }
+}
+
 source_set("txt") {
   defines = []
   if (flutter_use_fontconfig) {
@@ -296,6 +304,8 @@ executable("txt_unittests") {
     ]
   }
 
+  configs += [ ":allow_posix_names" ]
+
   deps = [
            ":txt",
            ":txt_test_utils",