diff --git a/src/compiler/sema_builtins.c b/src/compiler/sema_builtins.c
index 0def5c4a9..b4adea753 100644
--- a/src/compiler/sema_builtins.c
+++ b/src/compiler/sema_builtins.c
@@ -215,14 +215,21 @@ static bool sema_expr_analyse_compare_exchange(SemaContext *context, Expr *expr)
 	Expr *pointer = args[0];
 
 	if (!sema_analyse_expr(context, pointer)) return false;
+
 	bool optional = IS_OPTIONAL(pointer);
 	Type *comp_type = type_flatten(pointer->type);
 	if (!type_is_pointer(comp_type)) RETURN_SEMA_ERROR(pointer, "Expected a pointer here.");
-
 	Type *pointee = comp_type->pointer;
 	for (int i = 1; i < 3; i++)
 	{
-		if (!sema_analyse_expr_rhs(context, pointee, args[i], true)) return false;
+		Expr *arg = args[i];
+		if (!sema_analyse_expr_rhs(context, pointee == type_void ? NULL : pointee, arg, true)) return false;
+		if (pointee == type_void) pointee = arg->type->canonical;
+		if (!type_is_atomic(type_flatten(arg->type)))
+		{
+			RETURN_SEMA_ERROR(arg, "%s may not be used with atomics.", type_quoted_error_string(arg->type));
+		}
+
 		optional = optional || IS_OPTIONAL(args[i]);
 	}
 	for (int i = 3; i < 5; i++)
diff --git a/src/compiler/target.c b/src/compiler/target.c
index d5af3e636..938d4ce6f 100644
--- a/src/compiler/target.c
+++ b/src/compiler/target.c
@@ -459,7 +459,7 @@ static void x86features_as_diff_to_scratch(X86Features *cpu_features, X86CpuSet
 			x86_features_add_feature(&diff, X86_FEAT_CMPXCHG8B);
 			break;
 	}
-	for (int i = 0; i <= X86_FEATURE_LAST; i++)
+	for (X86Feature i = 0; i <= X86_FEATURE_LAST; i++)
 	{
 		if (i == X86_FEAT_AVX5124FMAPS || i == X86_FEAT_AVX5124VNNIW) continue;
 		bool diff_has = x64features_contains(&diff, (X86Feature)i);
diff --git a/src/version.h b/src/version.h
index 6c85acc93..53c647863 100644
--- a/src/version.h
+++ b/src/version.h
@@ -1 +1 @@
-#define COMPILER_VERSION "0.4.648"
\ No newline at end of file
+#define COMPILER_VERSION "0.4.649"
\ No newline at end of file