diff --git a/rai/core_test/interface.cpp b/rai/core_test/interface.cpp
index 99c60048..d7197294 100644
--- a/rai/core_test/interface.cpp
+++ b/rai/core_test/interface.cpp
@@ -7,6 +7,14 @@
 #include <rai/lib/numbers.hpp>
 #include <rai/lib/work.hpp>
 
+TEST (interface, xrb_uint128_to_dec)
+{
+	rai::uint128_union zero (0);
+	char text[40] = { 0 };
+	xrb_uint128_to_dec (zero.bytes.data (), text);
+	ASSERT_STREQ ("0", text);
+}
+
 TEST (interface, xrb_uint256_to_string)
 {
 	rai::uint256_union zero (0);
@@ -31,6 +39,14 @@ TEST (interface, xrb_uint512_to_string)
 	ASSERT_STREQ ("00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000", text);
 }
 
+TEST (interface, xrb_uint128_from_dec)
+{
+	rai::uint128_union zero (0);
+	ASSERT_EQ (0, xrb_uint128_from_dec ("340282366920938463463374607431768211455", zero.bytes.data ()));
+	ASSERT_EQ (1, xrb_uint128_from_dec ("340282366920938463463374607431768211456", zero.bytes.data ()));
+	ASSERT_EQ (1, xrb_uint128_from_dec ("3402823669209384634633%4607431768211455", zero.bytes.data ()));
+}
+
 TEST (interface, xrb_uint256_from_string)
 {
 	rai::uint256_union zero (0);
diff --git a/rai/core_test/uint256_union.cpp b/rai/core_test/uint256_union.cpp
index a8877cd8..79090e2d 100644
--- a/rai/core_test/uint256_union.cpp
+++ b/rai/core_test/uint256_union.cpp
@@ -37,6 +37,14 @@ TEST (uint128_union, decode_dec_leading_zero)
 	ASSERT_TRUE (error);
 }
 
+TEST (uint128_union, decode_dec_overflow)
+{
+	rai::uint128_union value;
+	std::string text ("340282366920938463463374607431768211456");
+	auto error (value.decode_dec (text));
+	ASSERT_TRUE (error);
+}
+
 struct test_punct : std::moneypunct<char>
 {
 	pattern do_pos_format () const
diff --git a/rai/lib/interface.cpp b/rai/lib/interface.cpp
index dba6dd2a..fe453dff 100644
--- a/rai/lib/interface.cpp
+++ b/rai/lib/interface.cpp
@@ -15,6 +15,12 @@
 #include <cstring>
 
 extern "C" {
+void xrb_uint128_to_dec (xrb_uint128 source, char * destination)
+{
+	auto const & number (*reinterpret_cast<rai::uint128_union *> (source));
+	strncpy (destination, number.to_string_dec ().c_str (), 32);
+}
+
 void xrb_uint256_to_string (xrb_uint256 source, char * destination)
 {
 	auto const & number (*reinterpret_cast<rai::uint256_union *> (source));
@@ -33,6 +39,13 @@ void xrb_uint512_to_string (xrb_uint512 source, char * destination)
 	strncpy (destination, number.to_string ().c_str (), 128);
 }
 
+int xrb_uint128_from_dec (const char * source, xrb_uint128 destination)
+{
+	auto & number (*reinterpret_cast<rai::uint128_union *> (destination));
+	auto error (number.decode_dec (source));
+	return error ? 1 : 0;
+}
+
 int xrb_uint256_from_string (const char * source, xrb_uint256 destination)
 {
 	auto & number (*reinterpret_cast<rai::uint256_union *> (destination));
diff --git a/rai/lib/interface.h b/rai/lib/interface.h
index d16db966..457891dc 100644
--- a/rai/lib/interface.h
+++ b/rai/lib/interface.h
@@ -5,10 +5,13 @@
 extern "C" {
 #endif
 
+typedef unsigned char * xrb_uint128; // 16byte array for public and private keys
 typedef unsigned char * xrb_uint256; // 32byte array for public and private keys
 typedef unsigned char * xrb_uint512; // 64byte array for signatures
 typedef void * xrb_transaction;
 
+// Convert amount bytes 'source' to a 39 byte not-null-terminated decimal string 'destination'
+void xrb_uint128_to_dec (const xrb_uint128 source, char * destination);
 // Convert public/private key bytes 'source' to a 64 byte not-null-terminated hex string 'destination'
 void xrb_uint256_to_string (const xrb_uint256 source, char * destination);
 // Convert public key bytes 'source' to a 65 byte non-null-terminated account string 'destination'
@@ -16,6 +19,9 @@ void xrb_uint256_to_address (xrb_uint256 source, char * destination);
 // Convert public/private key bytes 'source' to a 128 byte not-null-terminated hex string 'destination'
 void xrb_uint512_to_string (const xrb_uint512 source, char * destination);
 
+// Convert 39 byte decimal string 'source' to a byte array 'destination'
+// Return 0 on success, nonzero on error
+int xrb_uint128_from_dec (const char * source, xrb_uint128 destination);
 // Convert 64 byte hex string 'source' to a byte array 'destination'
 // Return 0 on success, nonzero on error
 int xrb_uint256_from_string (const char * source, xrb_uint256 destination);
diff --git a/rai/lib/numbers.cpp b/rai/lib/numbers.cpp
index 7eff825b..e2aee857 100644
--- a/rai/lib/numbers.cpp
+++ b/rai/lib/numbers.cpp
@@ -562,11 +562,12 @@ bool rai::uint128_union::decode_dec (std::string const & text)
 	{
 		std::stringstream stream (text);
 		stream << std::dec << std::noshowbase;
-		rai::uint128_t number_l;
+		boost::multiprecision::checked_uint128_t number_l;
 		try
 		{
 			stream >> number_l;
-			*this = number_l;
+			rai::uint128_t unchecked (number_l);
+			*this = unchecked;
 			if (!stream.eof ())
 			{
 				error = true;