diff --git a/Zend/tests/type_declarations/union_types/redundant_types/bool_instead_false_and_true.phpt b/Zend/tests/type_declarations/union_types/redundant_types/bool_instead_false_and_true.phpt
index 7386f4aa76735..f95214ce11686 100644
--- a/Zend/tests/type_declarations/union_types/redundant_types/bool_instead_false_and_true.phpt
+++ b/Zend/tests/type_declarations/union_types/redundant_types/bool_instead_false_and_true.phpt
@@ -8,4 +8,4 @@ function test(): false|true {
 
 ?>
 --EXPECTF--
-Fatal error: Type contains both true and false, bool should be used instead in %s on line %d
+Fatal error: Type contains both true and false, bool must be used instead in %s on line %d
diff --git a/Zend/tests/type_declarations/union_types/redundant_types/bool_instead_true_and_false.phpt b/Zend/tests/type_declarations/union_types/redundant_types/bool_instead_true_and_false.phpt
index 3dacf3e5dbdf5..a54c69f91fe72 100644
--- a/Zend/tests/type_declarations/union_types/redundant_types/bool_instead_true_and_false.phpt
+++ b/Zend/tests/type_declarations/union_types/redundant_types/bool_instead_true_and_false.phpt
@@ -8,4 +8,4 @@ function test(): true|false {
 
 ?>
 --EXPECTF--
-Fatal error: Type contains both true and false, bool should be used instead in %s on line %d
+Fatal error: Type contains both true and false, bool must be used instead in %s on line %d
diff --git a/Zend/zend_compile.c b/Zend/zend_compile.c
index cee7ec4361d69..112540929f8bb 100644
--- a/Zend/zend_compile.c
+++ b/Zend/zend_compile.c
@@ -6852,7 +6852,7 @@ static zend_type zend_compile_typename_ex(
 			if ( ((type_mask & MAY_BE_TRUE) && (single_type_mask == MAY_BE_FALSE))
 					|| ((type_mask & MAY_BE_FALSE) && (single_type_mask == MAY_BE_TRUE)) ) {
 				zend_error_noreturn(E_COMPILE_ERROR,
-					"Type contains both true and false, bool should be used instead");
+					"Type contains both true and false, bool must be used instead");
 			}
 			ZEND_TYPE_FULL_MASK(type) |= ZEND_TYPE_PURE_MASK(single_type);
 			ZEND_TYPE_FULL_MASK(single_type) &= ~_ZEND_TYPE_MAY_BE_MASK;