diff --git a/frame/contracts/src/wasm/mod.rs b/frame/contracts/src/wasm/mod.rs
index e81b94bf53127..7c98ee7cf5b1a 100644
--- a/frame/contracts/src/wasm/mod.rs
+++ b/frame/contracts/src/wasm/mod.rs
@@ -2281,7 +2281,7 @@ mod tests {
 "#;
 		let output = execute(CODE_IS_CONTRACT, vec![], MockExt::default()).unwrap();
 
-		// The mock ext just returns the same data that was passed as the subject.
+		// The mock ext just always returns 1u32 (`true`).
 		assert_eq!(
 			output,
 			ExecReturnValue { flags: ReturnFlags::empty(), data: Bytes(1u32.encode()) },
@@ -2294,18 +2294,20 @@ mod tests {
 		const CODE_CALLER_IS_ORIGIN: &str = r#"
 ;; This runs `caller_is_origin` check on zero account address
 (module
-	(import "__unstable__" "seal_caller_is_origin" (func $seal_is_contract (result i32)))
+	(import "__unstable__" "seal_caller_is_origin" (func $seal_caller_is_origin (result i32)))
 	(import "seal0" "seal_return" (func $seal_return (param i32 i32 i32)))
 	(import "env" "memory" (memory 1 1))
 
-	;; [0, 4) here we store the return code of the `seal_caller_is_origin`
+	;; [0, 4) here the return code of the `seal_caller_is_origin` will be stored
+	;; we initialize it with non-zero value to be sure that it's being overwritten below
+	(data (i32.const 0) "\10\10\10\10")
 
 	(func (export "deploy"))
 
 	(func (export "call")
 		(i32.store
-			(i32.const 4)
-			(call $seal_is_contract)
+			(i32.const 0)
+			(call $seal_caller_is_origin)
 		)
 		;; exit with success and take `seal_caller_is_origin` return code to the output buffer
 		(call $seal_return (i32.const 0) (i32.const 0) (i32.const 4))
@@ -2314,7 +2316,7 @@ mod tests {
 "#;
 		let output = execute(CODE_CALLER_IS_ORIGIN, vec![], MockExt::default()).unwrap();
 
-		// The mock ext just returns the same data that was passed as the subject.
+		// The mock ext just always returns 0u32 (`false`)
 		assert_eq!(
 			output,
 			ExecReturnValue { flags: ReturnFlags::empty(), data: Bytes(0u32.encode()) },