Index: lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD_x86_64.cpp
===================================================================
--- lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD_x86_64.cpp
+++ lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD_x86_64.cpp
@@ -894,33 +894,43 @@
 #endif
   case lldb_fctrl_x86_64:
     m_xstate.xs_fxsave.fx_cw = reg_value.GetAsUInt16();
+    m_xstate.xs_xstate_bv |= XCR0_X87;
     break;
   case lldb_fstat_x86_64:
     m_xstate.xs_fxsave.fx_sw = reg_value.GetAsUInt16();
+    m_xstate.xs_xstate_bv |= XCR0_X87;
     break;
   case lldb_ftag_x86_64:
     m_xstate.xs_fxsave.fx_tw = reg_value.GetAsUInt16();
+    m_xstate.xs_xstate_bv |= XCR0_X87;
     break;
   case lldb_fop_x86_64:
     m_xstate.xs_fxsave.fx_opcode = reg_value.GetAsUInt16();
+    m_xstate.xs_xstate_bv |= XCR0_X87;
     break;
   case lldb_fiseg_x86_64:
     m_xstate.xs_fxsave.fx_ip.fa_32.fa_seg = reg_value.GetAsUInt32();
+    m_xstate.xs_xstate_bv |= XCR0_X87;
     break;
   case lldb_fioff_x86_64:
     m_xstate.xs_fxsave.fx_ip.fa_32.fa_off = reg_value.GetAsUInt32();
+    m_xstate.xs_xstate_bv |= XCR0_X87;
     break;
   case lldb_foseg_x86_64:
     m_xstate.xs_fxsave.fx_dp.fa_32.fa_seg = reg_value.GetAsUInt32();
+    m_xstate.xs_xstate_bv |= XCR0_X87;
     break;
   case lldb_fooff_x86_64:
     m_xstate.xs_fxsave.fx_dp.fa_32.fa_off = reg_value.GetAsUInt32();
+    m_xstate.xs_xstate_bv |= XCR0_X87;
     break;
   case lldb_mxcsr_x86_64:
     m_xstate.xs_fxsave.fx_mxcsr = reg_value.GetAsUInt32();
+    m_xstate.xs_xstate_bv |= XCR0_SSE;
     break;
   case lldb_mxcsrmask_x86_64:
     m_xstate.xs_fxsave.fx_mxcsr_mask = reg_value.GetAsUInt32();
+    m_xstate.xs_xstate_bv |= XCR0_SSE;
     break;
   case lldb_st0_x86_64:
   case lldb_st1_x86_64:
@@ -932,6 +942,7 @@
   case lldb_st7_x86_64:
     ::memcpy(&m_xstate.xs_fxsave.fx_87_ac[reg - lldb_st0_x86_64],
              reg_value.GetBytes(), reg_value.GetByteSize());
+    m_xstate.xs_xstate_bv |= XCR0_X87;
     break;
   case lldb_mm0_x86_64:
   case lldb_mm1_x86_64:
@@ -943,6 +954,7 @@
   case lldb_mm7_x86_64:
     ::memcpy(&m_xstate.xs_fxsave.fx_87_ac[reg - lldb_mm0_x86_64],
              reg_value.GetBytes(), reg_value.GetByteSize());
+    m_xstate.xs_xstate_bv |= XCR0_X87;
     break;
   case lldb_xmm0_x86_64:
   case lldb_xmm1_x86_64:
@@ -966,6 +978,7 @@
     } else {
       ::memcpy(&m_xstate.xs_fxsave.fx_xmm[reg - lldb_xmm0_x86_64],
                reg_value.GetBytes(), reg_value.GetByteSize());
+      m_xstate.xs_xstate_bv |= XCR0_SSE;
     }
     break;
   case lldb_ymm0_x86_64:
@@ -994,6 +1007,7 @@
       ::memcpy(ymm.bytes, reg_value.GetBytes(), reg_value.GetByteSize());
       YMMToXState(ymm, m_xstate.xs_fxsave.fx_xmm[reg_index].xmm_bytes,
                   m_xstate.xs_ymm_hi128.xs_ymm[reg_index].ymm_bytes);
+      m_xstate.xs_xstate_bv |= XCR0_SSE | XCR0_YMM_Hi128;
     }
     break;
   case lldb_dr0_x86_64: