diff --git a/evmcc/Compiler.cpp b/evmcc/Compiler.cpp
index d5f39e053..f327f86ed 100644
--- a/evmcc/Compiler.cpp
+++ b/evmcc/Compiler.cpp
@@ -290,8 +290,8 @@ std::unique_ptr<llvm::Module> Compiler::compile(const dev::bytes& bytecode)
 		{
 			auto top = stack.pop();
 			auto zero = ConstantInt::get(Types.word256, 0);
-			auto nonzero = builder.CreateICmpNE(top, zero, "nonzero");
-			auto result = builder.CreateZExt(nonzero, Types.word256);
+			auto iszero = builder.CreateICmpEQ(top, zero, "iszero");
+			auto result = builder.CreateZExt(iszero, Types.word256);
 			stack.push(result);
 			break;
 		}
diff --git a/evmcc/bytecode/when1.evm b/evmcc/bytecode/when1.evm
new file mode 100644
index 000000000..303b02623
--- /dev/null
+++ b/evmcc/bytecode/when1.evm
@@ -0,0 +1 @@
+60010f600b59600d608054
diff --git a/evmcc/lll/when1.asm b/evmcc/lll/when1.asm
new file mode 100644
index 000000000..01d41c266
--- /dev/null
+++ b/evmcc/lll/when1.asm
@@ -0,0 +1,10 @@
+.code:
+  PUSH 1
+  NOT
+  PUSH [tag0]
+  JUMPI
+  PUSH 13
+  PUSH 128
+  MSTORE
+tag0: 
+
diff --git a/evmcc/lll/when1.lll b/evmcc/lll/when1.lll
new file mode 100644
index 000000000..990a6e64a
--- /dev/null
+++ b/evmcc/lll/when1.lll
@@ -0,0 +1,2 @@
+(when (> 1 0) [i] 13)
+ 
\ No newline at end of file