diff --git a/releasenotes.md b/releasenotes.md
index c06363dd9..dba3e8d8f 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -100,6 +100,7 @@
 - `int? ?` was not correctly handled. #2786
 - Casting const bytes to vector with different element size was broken #2787
 - Unable to access fields of a const inline enum with an aggregate underlying type. #2802
+- Using an optional type as generic parameter was not properly caught #2799
 
 ### Stdlib changes
 - Add `ThreadPool` join function to wait for all threads to finish in the pool without destroying the threads.
diff --git a/src/compiler/sema_decls.c b/src/compiler/sema_decls.c
index 7cb943950..b3b7d1c72 100644
--- a/src/compiler/sema_decls.c
+++ b/src/compiler/sema_decls.c
@@ -5438,6 +5438,10 @@ Decl *sema_analyse_parameterized_identifier(SemaContext *context, Path *decl_pat
 				return poisoned_decl;
 			}
 			Type *type = param->const_expr.typeid;
+			if (type_is_optional(type))
+			{
+				RETURN_VAL_SEMA_ERROR(poisoned_decl, param, "The generic type can never be an optional, please use only non-optional types.");
+			}
 			if (type_is_func_ptr(type))
 			{
 				if (!sema_resolve_type_decl(context, type->pointer)) return poisoned_decl;
@@ -5447,18 +5451,20 @@ Decl *sema_analyse_parameterized_identifier(SemaContext *context, Path *decl_pat
 		{
 			if (is_type)
 			{
-				SEMA_ERROR(param, "Expected a type, not a value, for parameter '%s'.", param_name);
-				return poisoned_decl;
+				RETURN_VAL_SEMA_ERROR(poisoned_decl, param, "Expected a type, not a value, for parameter '%s'.", param_name);
 			}
 			if (!sema_analyse_ct_expr(context, param)) return poisoned_decl;
 			Type *type = param->type->canonical;
 			if (type->type_kind == TYPE_TYPEDEF) type = type_flatten(type);
+			if (IS_OPTIONAL(param))
+			{
+				RETURN_VAL_SEMA_ERROR(poisoned_decl, param, "The parameter may never be an optional value.");
+			}
 
 			bool is_enum_or_fault = type_kind_is_enum_or_fault(type->type_kind);
 			if (!type_is_integer_or_bool_kind(type) && !is_enum_or_fault)
 			{
-				SEMA_ERROR(param, "Only integer, bool, fault and enum values may be generic arguments.");
-				return poisoned_decl;
+				RETURN_VAL_SEMA_ERROR(poisoned_decl, param, "Only integer, bool, fault and enum values may be generic arguments.");
 			}
 			ASSERT(expr_is_const(param));
 		}
diff --git a/test/test_suite/generic/generic_param_opt.c3 b/test/test_suite/generic/generic_param_opt.c3
new file mode 100644
index 000000000..f38ff5ee2
--- /dev/null
+++ b/test/test_suite/generic/generic_param_opt.c3
@@ -0,0 +1,8 @@
+import std;
+
+alias Aa = List{Path?}; // #error: The generic type can never be an optional, please use only non-optional types
+
+fn int main()
+{
+	return 0;
+}
\ No newline at end of file