diff --git a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
--- a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
@@ -4341,8 +4341,19 @@
           // gdb_type could reference some flags type defined in XML.
           llvm::StringMap<std::unique_ptr<RegisterFlags>>::iterator it =
               registers_flags_types.find(gdb_type);
-          if (it != registers_flags_types.end())
-            reg_info.flags_type = it->second.get();
+          if (it != registers_flags_types.end()) {
+            auto flags_type = it->second.get();
+            if (reg_info.byte_size == flags_type->GetSize())
+              reg_info.flags_type = flags_type;
+            else
+              LLDB_LOGF(log,
+                        "ProcessGDBRemote::ParseRegisters Size of register "
+                        "flags %s (%d bytes) for "
+                        "register %s does not match the register size (%d "
+                        "bytes). Ignoring this set of flags.",
+                        flags_type->GetID().c_str(), flags_type->GetSize(),
+                        reg_info.name.AsCString(), reg_info.byte_size);
+          }
 
           // There's a slim chance that the gdb_type name is both a flags type
           // and a simple type. Just in case, look for that too (setting both
diff --git a/lldb/test/API/functionalities/gdb_remote_client/TestXMLRegisterFlags.py b/lldb/test/API/functionalities/gdb_remote_client/TestXMLRegisterFlags.py
--- a/lldb/test/API/functionalities/gdb_remote_client/TestXMLRegisterFlags.py
+++ b/lldb/test/API/functionalities/gdb_remote_client/TestXMLRegisterFlags.py
@@ -319,6 +319,20 @@
 
         self.expect("register read cpsr", substrs=["(C = 1)"])
 
+    @skipIfXmlSupportMissing
+    @skipIfRemote
+    def test_flags_register_size_mismatch(self):
+        # If the size of the flag set found does not match the size of the
+        # register, we discard the flags.
+        self.setup_register_test("""\
+          <flags id="cpsr_flags" size="8">
+            <field name="C" start="0" end="0"/>
+          </flags>
+          <reg name="pc" bitsize="64"/>
+          <reg name="cpsr" regnum="33" bitsize="32" type="cpsr_flags"/>""")
+
+        self.expect("register read cpsr", substrs=["(C = 1)"], matching=False)
+
     @skipIfXmlSupportMissing
     @skipIfRemote
     def test_flags_set_even_if_format_set(self):
@@ -439,7 +453,7 @@
             'core.xml' : dedent("""\
                 <?xml version="1.0"?>
                 <feature name="org.gnu.gdb.aarch64.core">
-                  <flags id="x0_flags" size="4">
+                  <flags id="x0_flags" size="8">
                     <field name="B" start="0" end="0"/>
                   </flags>
                   <reg name="pc" bitsize="64"/>
@@ -475,23 +489,23 @@
             'core.xml' : dedent("""\
                 <?xml version="1.0"?>
                 <feature name="org.gnu.gdb.aarch64.core">
-                  <flags id="my_flags" size="4">
+                  <flags id="my_flags" size="8">
                     <field name="correct" start="0" end="0"/>
                   </flags>
                   <reg name="pc" bitsize="64"/>
                   <reg name="x0" regnum="0" bitsize="64" type="my_flags"/>
                 </feature>"""),
-            # The my_flags here is ignored, so cpsr will use the my_flags from above.
+            # The my_flags here is ignored, so x1 will use the my_flags from above.
             'core-2.xml' : dedent("""\
                 <?xml version="1.0"?>
                 <feature name="org.gnu.gdb.aarch64.core">
-                  <flags id="my_flags" size="4">
+                  <flags id="my_flags" size="8">
                     <field name="incorrect" start="0" end="0"/>
                   </flags>
-                  <reg name="cpsr" regnum="33" bitsize="32" type="my_flags"/>
+                  <reg name="x1" regnum="33" bitsize="64" type="my_flags"/>
                 </feature>
             """),
         })
 
         self.expect("register read x0", substrs=["(correct = 1)"])
-        self.expect("register read cpsr", substrs=["(correct = 1)"])
+        self.expect("register read x1", substrs=["(correct = 1)"])