diff --git a/hw/intc/xive.c b/hw/intc/xive.c
index dc86a7a3be..0e81678ab3 100644
--- a/hw/intc/xive.c
+++ b/hw/intc/xive.c
@@ -742,6 +742,10 @@ void xive_tctx_reset(XiveTCTX *tctx)
     tctx->regs[TM_QW1_OS + TM_LSMFB] = 0xFF;
     tctx->regs[TM_QW1_OS + TM_ACK_CNT] = 0xFF;
     tctx->regs[TM_QW1_OS + TM_AGE] = 0xFF;
+    if (!(xive_presenter_get_config(tctx->xptr) &
+          XIVE_PRESENTER_GEN1_TIMA_OS)) {
+        tctx->regs[TM_QW1_OS + TM_OGEN] = 2;
+    }
 
     /*
      * Initialize PIPR to 0xFF to avoid phantom interrupts when the
diff --git a/include/hw/ppc/xive_regs.h b/include/hw/ppc/xive_regs.h
index 9d52d464d9..9062c6abf6 100644
--- a/include/hw/ppc/xive_regs.h
+++ b/include/hw/ppc/xive_regs.h
@@ -79,6 +79,7 @@
 #define TM_INC                  0x5  /*  -   +   -   +  */
 #define TM_AGE                  0x6  /*  -   +   -   +  */
 #define TM_PIPR                 0x7  /*  -   +   -   +  */
+#define TM_OGEN                 0xF  /*  -   +   -   -  */ /* P10 only */
 
 #define TM_WORD0                0x0
 #define TM_WORD1                0x4