diff --git a/xen/arch/x86/alternative.c b/xen/arch/x86/alternative.c
index 80c4dc721b..a4cadd9b0b 100644
--- a/xen/arch/x86/alternative.c
+++ b/xen/arch/x86/alternative.c
@@ -342,13 +342,13 @@ static int init_or_livepatch _apply_alternatives(struct alt_instr *start,
 
         /* 0xe8/0xe9 are relative branches; fix the offset. */
         if ( a->repl_len >= 5 && (*buf & 0xfe) == 0xe8 )
-            *(int32_t *)(buf + 1) += repl - orig;
+            *(int32_t *)(buf + 1) += (long)repl - (long)orig;
         else if ( IS_ENABLED(CONFIG_RETURN_THUNK) &&
                   a->repl_len > 5 && buf[a->repl_len - 5] == 0xe9 &&
                   ((long)repl + a->repl_len +
                    *(int32_t *)(buf + a->repl_len - 4) ==
                    (long)__x86_return_thunk) )
-            *(int32_t *)(buf + a->repl_len - 4) += repl - orig;
+            *(int32_t *)(buf + a->repl_len - 4) += (long)repl - (long)orig;
 
         a->priv = 1;