diff --git a/lldb/source/Utility/RegisterValue.cpp b/lldb/source/Utility/RegisterValue.cpp
index 0e99451c3b700..12c349a143c0f 100644
--- a/lldb/source/Utility/RegisterValue.cpp
+++ b/lldb/source/Utility/RegisterValue.cpp
@@ -199,7 +199,7 @@ Status RegisterValue::SetValueFromData(const RegisterInfo &reg_info,
     else if (reg_info.byte_size <= 16) {
       uint64_t data1 = src.GetU64(&src_offset);
       uint64_t data2 = src.GetU64(&src_offset);
-      if (src.GetByteOrder() == eByteOrderBig) {
+      if (src.GetByteOrder() == eByteOrderLittle) {
         int128.x[0] = data1;
         int128.x[1] = data2;
       } else {
diff --git a/lldb/unittests/Utility/RegisterValueTest.cpp b/lldb/unittests/Utility/RegisterValueTest.cpp
index e0863a41605e6..6239dbe21634a 100644
--- a/lldb/unittests/Utility/RegisterValueTest.cpp
+++ b/lldb/unittests/Utility/RegisterValueTest.cpp
@@ -7,6 +7,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "lldb/Utility/RegisterValue.h"
+#include "lldb/Utility/DataExtractor.h"
+#include "lldb/lldb-private-types.h"
 #include "gtest/gtest.h"
 #include <optional>
 
@@ -54,3 +56,41 @@ TEST(RegisterValueTest, GetScalarValue) {
             Scalar((APInt(128, 0xffeeddccbbaa9988ull) << 64) |
                    APInt(128, 0x7766554433221100)));
 }
+
+static const Scalar etalon128(APInt(128, 0xffeeddccbbaa9988ull) << 64 |
+                              APInt(128, 0x7766554433221100ull));
+
+void TestSetValueFromData128(void *src, const lldb::ByteOrder endianness) {
+  RegisterInfo ri{"uint128_register",
+                  nullptr,
+                  16,
+                  0,
+                  lldb::Encoding::eEncodingUint,
+                  lldb::Format::eFormatDefault,
+                  {0, 0, 0, LLDB_INVALID_REGNUM, 0},
+                  nullptr,
+                  nullptr,
+                  nullptr};
+  DataExtractor src_extractor(src, 16, endianness, 8);
+  RegisterValue rv;
+  EXPECT_TRUE(rv.SetValueFromData(ri, src_extractor, 0, false).Success());
+  Scalar s;
+  EXPECT_TRUE(rv.GetScalarValue(s));
+  EXPECT_EQ(s, etalon128);
+}
+
+// Test that the "RegisterValue::SetValueFromData" method works correctly
+// with 128-bit little-endian data that represents an integer.
+TEST(RegisterValueTest, SetValueFromData_128_le) {
+  uint8_t src[] = {0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
+                   0x88, 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff};
+  TestSetValueFromData128(src, lldb::ByteOrder::eByteOrderLittle);
+}
+
+// Test that the "RegisterValue::SetValueFromData" method works correctly
+// with 128-bit big-endian data that represents an integer.
+TEST(RegisterValueTest, SetValueFromData_128_be) {
+  uint8_t src[] = {0xff, 0xee, 0xdd, 0xcc, 0xbb, 0xaa, 0x99, 0x88,
+                   0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11, 0x00};
+  TestSetValueFromData128(src, lldb::ByteOrder::eByteOrderBig);
+}