diff --git a/SPIRV/spvIR.h b/SPIRV/spvIR.h
index 660742a7..5cbffec2 100644
--- a/SPIRV/spvIR.h
+++ b/SPIRV/spvIR.h
@@ -97,6 +97,8 @@ public:
     explicit Instruction(Op opCode) : resultId(NoResult), typeId(NoType), opCode(opCode), block(nullptr) { }
     virtual ~Instruction() {}
     void addIdOperand(Id id) {
+        // ids can't be 0
+        assert(id);
         operands.push_back(id);
         idOperand.push_back(true);
     }