diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index e2f697779..afa6ffdf6 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -184,7 +184,7 @@ jobs:
       fail-fast: false
       matrix:
         build_type: [Release, Debug]
-        llvm_version: [16, 17]
+        llvm_version: [15, 16]
 
     steps:
       - uses: actions/checkout@v3
diff --git a/src/compiler/sema_expr.c b/src/compiler/sema_expr.c
index 7e60c6210..4c147bf40 100644
--- a/src/compiler/sema_expr.c
+++ b/src/compiler/sema_expr.c
@@ -7337,7 +7337,7 @@ bool sema_analyse_expr_rhs(SemaContext *context, Type *to, Expr *expr, bool allo
 		Type *flat = type_flatten(to);
 		if (flat != type_anyfault && flat->type_kind != TYPE_FAULTTYPE && expr->expr_kind == EXPR_CONST)
 		{
-			sema_error_at_after(expr->span, "You need to add a trailing '!' here to make this an optional.");
+			sema_error_at_after(expr->span, "You need to add a trailing '?' here to make this an optional.");
 			return false;
 		}
 	}
diff --git a/src/version.h b/src/version.h
index 862dcafe1..0a403ab1b 100644
--- a/src/version.h
+++ b/src/version.h
@@ -1 +1 @@
-#define COMPILER_VERSION "0.4.506"
\ No newline at end of file
+#define COMPILER_VERSION "0.4.507"
\ No newline at end of file