diff --git a/build/docker/ubuntu-bionic/Dockerfile b/build/docker/ubuntu-bionic/Dockerfile
index 291aa5d..0407a6f 100644
--- a/build/docker/ubuntu-bionic/Dockerfile
+++ b/build/docker/ubuntu-bionic/Dockerfile
@@ -253,6 +253,13 @@
     rm swift-5.1.4-RELEASE-ubuntu18.04.tar.gz && \
     swift --version
 
+# Locale(s) for cpp unit tests
+RUN apt-get install -y --no-install-recommends \
+`# Locale dependencies` \
+      locales && \
+    locale-gen en_US.UTF-8 && \
+    update-locale
+
 # cppcheck-1.82 has a nasty cpp parser bug, so we're using something newer
 RUN apt-get install -y --no-install-recommends \
 `# Static Code Analysis dependencies` \
diff --git a/build/docker/ubuntu-disco/Dockerfile b/build/docker/ubuntu-disco/Dockerfile
index 9775fbb..a175ed5 100644
--- a/build/docker/ubuntu-disco/Dockerfile
+++ b/build/docker/ubuntu-disco/Dockerfile
@@ -255,6 +255,13 @@
 #     rm swift-4.2.1-RELEASE-ubuntu18.04.tar.gz && \
 #     swift --version
 
+# Locale(s) for cpp unit tests
+RUN apt-get install -y --no-install-recommends \
+`# Locale dependencies` \
+      locales && \
+    locale-gen en_US.UTF-8 && \
+    update-locale
+
 # cppcheck-1.82 has a nasty cpp parser bug, so we're using something newer
 # don't need this on disco, nobody uses it
 # RUN apt-get install -y --no-install-recommends \
diff --git a/build/docker/ubuntu-xenial/Dockerfile b/build/docker/ubuntu-xenial/Dockerfile
index 62da2c4..1c4373e 100644
--- a/build/docker/ubuntu-xenial/Dockerfile
+++ b/build/docker/ubuntu-xenial/Dockerfile
@@ -235,6 +235,13 @@
 # Rust dependencies
 RUN curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain 1.40.0 -y
 
+# Locale(s) for cpp unit tests
+RUN apt-get install -y --no-install-recommends \
+`# Locale dependencies` \
+      locales && \
+    locale-gen en_US.UTF-8 && \
+    update-locale
+
 # Clean up
 RUN rm -rf /var/cache/apt/* && \
     rm -rf /var/lib/apt/lists/* && \
diff --git a/lib/cpp/src/thrift/TToString.h b/lib/cpp/src/thrift/TToString.h
index 25780f9..fbeac51 100644
--- a/lib/cpp/src/thrift/TToString.h
+++ b/lib/cpp/src/thrift/TToString.h
@@ -22,6 +22,7 @@
 
 #include <cmath>
 #include <limits>
+#include <locale>
 #include <map>
 #include <set>
 #include <sstream>
@@ -34,6 +35,7 @@
 template <typename T>
 std::string to_string(const T& t) {
   std::ostringstream o;
+  o.imbue(std::locale("C"));
   o << t;
   return o.str();
 }
diff --git a/lib/cpp/test/JSONProtoTest.cpp b/lib/cpp/test/JSONProtoTest.cpp
index 082c8a2..6d1cd8c 100644
--- a/lib/cpp/test/JSONProtoTest.cpp
+++ b/lib/cpp/test/JSONProtoTest.cpp
@@ -22,6 +22,7 @@
 #include <iomanip>
 #include <sstream>
 #include <thrift/protocol/TJSONProtocol.h>
+#include <locale>
 #include <memory>
 #include <thrift/transport/TBufferTransports.h>
 #include "gen-cpp/DebugProtoTest_types.h"
@@ -350,3 +351,26 @@
   BOOST_CHECK_THROW(ooe2.read(proto.get()),
     apache::thrift::protocol::TProtocolException);
 }
+
+BOOST_AUTO_TEST_CASE(test_json_locale_with_thousands_separator_comma) {
+  testCaseSetup_1();
+
+  const std::string expected_result(
+  "{\"1\":{\"tf\":1},\"2\":{\"tf\":0},\"3\":{\"i8\":127},\"4\":{\"i16\":27000},"
+  "\"5\":{\"i32\":16777216},\"6\":{\"i64\":6000000000},\"7\":{\"dbl\":3.1415926"
+  "535897931},\"8\":{\"str\":\"JSON THIS! \\\"\\u0001\"},\"9\":{\"str\":\"\xd7\\"
+  "n\\u0007\\t\"},\"10\":{\"tf\":0},\"11\":{\"str\":\"AQIDrQ\"},\"12\":{\"lst\""
+  ":[\"i8\",3,1,2,3]},\"13\":{\"lst\":[\"i16\",3,1,2,3]},\"14\":{\"lst\":[\"i64"
+  "\",3,1,2,3]}}");
+
+#if _WIN32
+  std::locale::global(std::locale("en-US.UTF-8"));
+#else
+  std::locale::global(std::locale("en_US.UTF-8"));
+#endif
+
+  const std::string result(apache::thrift::ThriftJSONString(*ooe));
+
+  BOOST_CHECK_MESSAGE(!expected_result.compare(result),
+    "Expected:\n" << expected_result << "\nGotten:\n" << result);
+}