diff --git a/irdb-libs/libIRDB-core/src/operand_csx86.cpp b/irdb-libs/libIRDB-core/src/operand_csx86.cpp
index f7c4216079ecdb3d17ca2906cff2da76e31fe4da..a6dd22caa5d1267f514b803951456937e2848a2c 100644
--- a/irdb-libs/libIRDB-core/src/operand_csx86.cpp
+++ b/irdb-libs/libIRDB-core/src/operand_csx86.cpp
@@ -176,6 +176,9 @@ static uint32_t to_reg_number(const x86_reg &reg)
 		case X86_REG_R15D:
 		case X86_REG_R15W:
 			return 15;
+        case X86_REG_RIZ:
+        case X86_REG_EIZ:
+            return -1; // STARS_x86_R_none, RIZ/EIZ is a pseudo-register having constant value of 0
 		default: break;
 	}
 	assert(0);