diff --git a/lldb/source/Commands/CommandObjectPlatform.cpp b/lldb/source/Commands/CommandObjectPlatform.cpp
--- a/lldb/source/Commands/CommandObjectPlatform.cpp
+++ b/lldb/source/Commands/CommandObjectPlatform.cpp
@@ -589,11 +589,15 @@
       }
       std::string buffer(m_options.m_count, 0);
       Status error;
-      uint32_t retcode = platform_sp->ReadFile(
+      uint64_t retcode = platform_sp->ReadFile(
           fd, m_options.m_offset, &buffer[0], m_options.m_count, error);
-      result.AppendMessageWithFormat("Return = %d\n", retcode);
-      result.AppendMessageWithFormat("Data = \"%s\"\n", buffer.c_str());
-      result.SetStatus(eReturnStatusSuccessFinishResult);
+      if (retcode != UINT64_MAX) {
+        result.AppendMessageWithFormat("Return = %" PRIu64 "\n", retcode);
+        result.AppendMessageWithFormat("Data = \"%s\"\n", buffer.c_str());
+        result.SetStatus(eReturnStatusSuccessFinishResult);
+      } else {
+        result.AppendError(error.AsCString());
+      }
     } else {
       result.AppendError("no platform currently selected\n");
     }
@@ -678,11 +682,15 @@
                                       cmd_line);
         return result.Succeeded();
       }
-      uint32_t retcode =
+      uint64_t retcode =
           platform_sp->WriteFile(fd, m_options.m_offset, &m_options.m_data[0],
                                  m_options.m_data.size(), error);
-      result.AppendMessageWithFormat("Return = %d\n", retcode);
-      result.SetStatus(eReturnStatusSuccessFinishResult);
+      if (retcode != UINT64_MAX) {
+        result.AppendMessageWithFormat("Return = %" PRIu64 "\n", retcode);
+        result.SetStatus(eReturnStatusSuccessFinishResult);
+      } else {
+        result.AppendError(error.AsCString());
+      }
     } else {
       result.AppendError("no platform currently selected\n");
     }
diff --git a/lldb/test/API/functionalities/gdb_remote_client/TestGDBRemotePlatformFile.py b/lldb/test/API/functionalities/gdb_remote_client/TestGDBRemotePlatformFile.py
--- a/lldb/test/API/functionalities/gdb_remote_client/TestGDBRemotePlatformFile.py
+++ b/lldb/test/API/functionalities/gdb_remote_client/TestGDBRemotePlatformFile.py
@@ -60,11 +60,12 @@
             self.match("platform file open /some/file.txt -v 0755",
                        [r"error: Invalid argument"],
                        error=True)
-            # TODO: fix the commands to fail on unsuccessful result
             self.match("platform file read 16 -o 11 -c 13",
-                       [r"Return = -1\nData = \"\""])
+                       [r"error: Invalid argument"],
+                       error=True)
             self.match("platform file write 16 -o 11 -d teststring",
-                       [r"Return = -1"])
+                       [r"error: Invalid argument"],
+                       error=True)
             self.match("platform file close 16",
                        [r"error: Invalid argument"],
                        error=True)