diff --git a/tools/qfcc/include/algebra.h b/tools/qfcc/include/algebra.h
index c87221eaf..ea67fcefc 100644
--- a/tools/qfcc/include/algebra.h
+++ b/tools/qfcc/include/algebra.h
@@ -82,8 +82,10 @@ typedef struct multivector_s {
 } multivector_t;
 
 struct expr_s;
+struct attribute_s;
 bool is_algebra (const struct type_s *type) __attribute__((pure));
 struct type_s *algebra_type (struct type_s *type, struct expr_s *params);
+struct type_s *algebra_subtype (struct type_s *type, struct attribute_s *attr);
 struct type_s *algebra_mvec_type (algebra_t *algebra, pr_uint_t group_mask);
 struct ex_value_s *algebra_blade_value (algebra_t *alg, const char *name);
 struct symtab_s *algebra_scope (struct type_s *type, struct symtab_s *curscope);
diff --git a/tools/qfcc/source/algebra.c b/tools/qfcc/source/algebra.c
index 84da21efa..d03ca4fbe 100644
--- a/tools/qfcc/source/algebra.c
+++ b/tools/qfcc/source/algebra.c
@@ -37,6 +37,7 @@
 #include "QF/va.h"
 
 #include "tools/qfcc/include/algebra.h"
+#include "tools/qfcc/include/attribute.h"
 #include "tools/qfcc/include/diagnostic.h"
 #include "tools/qfcc/include/expr.h"
 #include "tools/qfcc/include/strpool.h"
@@ -412,6 +413,34 @@ algebra_type (type_t *type, expr_t *params)
 	return find_type (t);
 }
 
+type_t *
+algebra_subtype (type_t *type, attribute_t *attr)
+{
+	if (!is_algebra (type)) {
+		internal_error (0, "unexpected type");
+	}
+	auto algebra = algebra_get (type);
+	if (strcmp (attr->name, "group_mask") == 0) {
+		if (!attr->params || attr->params->next) {
+			error (0, "incorrect number of parameters to 'group_mask'");
+			return type;
+		}
+		auto param = attr->params;
+		if (!is_integral_val (param)) {
+			error (0, "'group_mask' parameter must be an integer constant");
+			return type;
+		}
+		pr_uint_t mask = expr_integral (param);
+		if (!mask || mask > ((1u << algebra->layout.count) - 1)) {
+			error (0, "invalid group_mask");
+			return type;
+		}
+		return algebra_mvec_type (algebra, mask);
+	}
+	return type;
+}
+
+
 type_t *
 algebra_mvec_type (algebra_t *algebra, pr_uint_t group_mask)
 {
diff --git a/tools/qfcc/source/qc-parse.y b/tools/qfcc/source/qc-parse.y
index 75951cf37..b5b62a583 100644
--- a/tools/qfcc/source/qc-parse.y
+++ b/tools/qfcc/source/qc-parse.y
@@ -894,7 +894,11 @@ typespec
 
 typespec_reserved
 	: TYPE_SPEC
-	| algebra_specifier
+	| algebra_specifier %prec LOW
+	| algebra_specifier '.' attribute
+		{
+			$$ = make_spec (algebra_subtype ($1.type, $3), 0, 0, 0);
+		}
 	| enum_specifier
 	| struct_specifier
 	// NOTE: fields don't parse the way they should. This is not a problem
@@ -907,9 +911,18 @@ typespec_reserved
 		}
 	;
 
-
 typespec_nonreserved
-	: TYPE_NAME
+	: TYPE_NAME %prec LOW
+	| TYPE_NAME '.' attribute
+		{
+			if (!is_algebra ($1.type)) {
+				error (0, "%s does not have any subtypes",
+					   get_type_string ($1.type));
+				$$ = $1;
+			} else {
+				$$ = make_spec (algebra_subtype ($1.type, $3), 0, 0, 0);
+			}
+		}
 	| OBJECT_NAME protocolrefs
 		{
 			if ($2) {
@@ -1015,7 +1028,7 @@ attribute_list
 	;
 
 attribute
-	: NAME						{ $$ = new_attribute ($1->name, 0); }
+	: NAME %prec LOW			{ $$ = new_attribute ($1->name, 0); }
 	| NAME '(' expr_list ')'	{ $$ = new_attribute ($1->name, $3); }
 	;
 
diff --git a/tools/qfcc/test/algtypes.r b/tools/qfcc/test/algtypes.r
index d227e006d..4c4f60572 100644
--- a/tools/qfcc/test/algtypes.r
+++ b/tools/qfcc/test/algtypes.r
@@ -1,3 +1,4 @@
+#include "test-harness.h"
 int foo[128];
 @algebra(float) pgaf1;
 //@algebra(double) pgad1;
@@ -13,16 +14,16 @@ typedef @algebra(float(4,1)) CGA;
 typedef @algebra(double(2,0,1)) PGA2;
 PGA2 pga2;
 
-float sin(float x) = #0;
-
 int
 main (void)
 {
+	PGA.group_mask (0x1) plane;
 	@algebra (PGA) {
 		auto p1 = 3*e1 + e2 - e3 + e0;
 		auto p2 = e1 + 3*e2 + e3 - e0;
 		auto v = 4*(e1 + e032 + e123);
 		pgaf1 = p1 + v * p2;
+		plane = p1;
 //		pgaf1 = (p1 + v)∧p2;
 //		pgaf1 = v • p2;
 #if 0
@@ -46,5 +47,6 @@ main (void)
 //		pga2 = p + (1 + p)∧l1;
 		pga2 = (l1 • p)*l1;
 	}
+	printf ("%q\n", plane);
 	return 0;		// to survive and prevail :)
 }