diff --git a/src/x87.c b/src/x87.c
index 176308a..88e043e 100644
--- a/src/x87.c
+++ b/src/x87.c
@@ -414,6 +414,10 @@ void x87_d9()
                         if (fplog) pclog("FNOP\n");
                         cycles-=3;
                         return;
+                        case 0xD8: case 0xD9: case 0xDA: case 0xDB: /*Invalid, but apparently not illegal*/
+                        case 0xDC: case 0xDD: case 0xDE: case 0xDF:
+                        cycles-=3;
+                        return;
                         case 0xE0: /*FCHS*/
                         if (fplog) pclog("FCHS\n");
                         ST(0)=-ST(0);