diff --git a/src/check_type.cpp b/src/check_type.cpp
index fe76d65d5..32309ce26 100644
--- a/src/check_type.cpp
+++ b/src/check_type.cpp
@@ -1662,6 +1662,10 @@ Type *check_get_params(CheckerContext *ctx, Scope *scope, Ast *_params, bool *is
 					error(name, "'auto_cast' can only be applied to variable fields");
 					p->flags &= ~FieldFlag_auto_cast;
 				}
+				if (p->flags&FieldFlag_const) {
+					error(name, "'#const' can only be applied to variable fields");
+					p->flags &= ~FieldFlag_const;
+				}
 
 				param = alloc_entity_type_name(scope, name->Ident.token, type, EntityState_Resolved);
 				param->TypeName.is_type_alias = true;
@@ -1726,6 +1730,10 @@ Type *check_get_params(CheckerContext *ctx, Scope *scope, Ast *_params, bool *is
 						error(name, "'auto_cast' can only be applied to variable fields");
 						p->flags &= ~FieldFlag_auto_cast;
 					}
+					if (p->flags&FieldFlag_const) {
+						error(name, "'#const' can only be applied to variable fields");
+						p->flags &= ~FieldFlag_const;
+					}
 
 					if (!is_type_constant_type(type) && !is_type_polymorphic(type)) {
 						gbString str = type_to_string(type);
@@ -1745,6 +1753,9 @@ Type *check_get_params(CheckerContext *ctx, Scope *scope, Ast *_params, bool *is
 			if (p->flags&FieldFlag_auto_cast) {
 				param->flags |= EntityFlag_AutoCast;
 			}
+			if (p->flags&FieldFlag_const) {
+				param->flags |= EntityFlag_ConstInput;
+			}
 
 			param->state = EntityState_Resolved; // NOTE(bill): This should have be resolved whilst determining it
 			add_entity(ctx->checker, scope, name, param);
diff --git a/src/parser.cpp b/src/parser.cpp
index 7d794a898..702ef6605 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -3127,6 +3127,7 @@ u32 parse_field_prefixes(AstFile *f) {
 	i32 no_alias_count  = 0;
 	i32 c_vararg_count  = 0;
 	i32 auto_cast_count = 0;
+	i32 const_count     = 0;
 
 	for (;;) {
 		FieldPrefixKind kind = is_token_field_prefix(f);
@@ -3144,12 +3145,14 @@ u32 parse_field_prefixes(AstFile *f) {
 		case FieldPrefix_no_alias:  no_alias_count  += 1; advance_token(f); break;
 		case FieldPrefix_c_var_arg: c_vararg_count  += 1; advance_token(f); break;
 		case FieldPrefix_auto_cast: auto_cast_count += 1; advance_token(f); break;
+		case FieldPrefix_const:     const_count += 1; advance_token(f); break;
 		}
 	}
 	if (using_count     > 1) syntax_error(f->curr_token, "Multiple 'using' in this field list");
 	if (no_alias_count  > 1) syntax_error(f->curr_token, "Multiple '#no_alias' in this field list");
 	if (c_vararg_count  > 1) syntax_error(f->curr_token, "Multiple '#c_vararg' in this field list");
 	if (auto_cast_count > 1) syntax_error(f->curr_token, "Multiple 'auto_cast' in this field list");
+	if (const_count > 1)     syntax_error(f->curr_token, "Multiple '#const' in this field list");
 
 
 	u32 field_flags = 0;
@@ -3157,6 +3160,7 @@ u32 parse_field_prefixes(AstFile *f) {
 	if (no_alias_count  > 0) field_flags |= FieldFlag_no_alias;
 	if (c_vararg_count  > 0) field_flags |= FieldFlag_c_vararg;
 	if (auto_cast_count > 0) field_flags |= FieldFlag_auto_cast;
+	if (const_count > 0)     field_flags |= FieldFlag_const;
 	return field_flags;
 }
 
diff --git a/src/parser.hpp b/src/parser.hpp
index 76ba5c04f..a98060df9 100644
--- a/src/parser.hpp
+++ b/src/parser.hpp
@@ -212,12 +212,13 @@ enum FieldFlag {
 	FieldFlag_no_alias  = 1<<2,
 	FieldFlag_c_vararg  = 1<<3,
 	FieldFlag_auto_cast = 1<<4,
+	FieldFlag_const     = 1<<5,
 
 	FieldFlag_Tags = 1<<10,
 
 	FieldFlag_Results   = 1<<16,
 
-	FieldFlag_Signature = FieldFlag_ellipsis|FieldFlag_using|FieldFlag_no_alias|FieldFlag_c_vararg|FieldFlag_auto_cast,
+	FieldFlag_Signature = FieldFlag_ellipsis|FieldFlag_using|FieldFlag_no_alias|FieldFlag_c_vararg|FieldFlag_auto_cast|FieldFlag_const,
 	FieldFlag_Struct    = FieldFlag_using|FieldFlag_Tags,
 };