diff --git a/src/arithops.c b/src/arithops.c
index 9bee65e..90faa30 100644
--- a/src/arithops.c
+++ b/src/arithops.c
@@ -313,7 +313,7 @@ LispPTR N_OP_makenumber(LispPTR tosm1, LispPTR tos) {
 
   if (((tosm1 & 0xFFFF0000) != S_POSITIVE) || ((tos & 0xFFFF0000) != S_POSITIVE)) ERROR_EXIT(tos);
   /* UB: left shift of 49152 by 16 places cannot be represented in type 'int' */
-  result = ((tosm1 & 0xffff) << 16) | (tos & 0xffff);
+  result = (int)(((tosm1 & 0xffff) << 16) | (tos & 0xffff));
   N_ARITH_SWITCH(result);
 } /* end OP_makenumber */