diff --git a/tools/qfcc/include/def.h b/tools/qfcc/include/def.h
index a00758bdf..a23f241d9 100644
--- a/tools/qfcc/include/def.h
+++ b/tools/qfcc/include/def.h
@@ -165,6 +165,9 @@ def_t *new_def (const char *name, struct type_s *type,
 	\todo Make aliasing to the same type a no-op?
 */
 def_t *alias_def (def_t *def, struct type_s *type, int offset);
+//FIXME this probably shouldn't exist (it's for swizzles, so doing proper
+//multi-width swizzles will remove the need for it)
+def_t *cover_alias_def (def_t *def, struct type_s *type, int offset);
 
 /** Free a def.
 
diff --git a/tools/qfcc/source/def.c b/tools/qfcc/source/def.c
index e48ccc948..69ee75198 100644
--- a/tools/qfcc/source/def.c
+++ b/tools/qfcc/source/def.c
@@ -179,20 +179,12 @@ new_def (const char *name, type_t *type, defspace_t *space,
 }
 
 def_t *
-alias_def (def_t *def, type_t *type, int offset)
+cover_alias_def (def_t *def, type_t *type, int offset)
 {
 	def_t      *alias;
 
-	if (def->alias) {
-		expr_t      e;
-		e.file = def->file;
-		e.line = def->line;
-		internal_error (&e, "aliasing an alias def");
-	}
-	if (type_size (type) > type_size (def->type))
-		internal_error (0, "aliasing a def to a larger type");
-	if (offset < 0 || offset + type_size (type) > type_size (def->type))
-		internal_error (0, "invalid alias offset");
+	if (offset + type_size (type) <= 0 || offset >= type_size (def->type))
+		internal_error (0, "invalid cover offset");
 	for (alias = def->alias_defs; alias; alias = alias->next) {
 		if (alias->type == type && alias->offset == offset)
 			return alias;
@@ -212,6 +204,22 @@ alias_def (def_t *def, type_t *type, int offset)
 	return alias;
 }
 
+def_t *
+alias_def (def_t *def, type_t *type, int offset)
+{
+	if (def->alias) {
+		expr_t      e;
+		e.file = def->file;
+		e.line = def->line;
+		internal_error (&e, "aliasing an alias def");
+	}
+	if (type_size (type) > type_size (def->type))
+		internal_error (0, "aliasing a def to a larger type");
+	if (offset < 0 || offset + type_size (type) > type_size (def->type))
+		internal_error (0, "invalid alias offset");
+	return cover_alias_def (def, type, offset);
+}
+
 def_t *
 temp_def (type_t *type)
 {
diff --git a/tools/qfcc/source/emit.c b/tools/qfcc/source/emit.c
index d5615a794..8e0045155 100644
--- a/tools/qfcc/source/emit.c
+++ b/tools/qfcc/source/emit.c
@@ -191,11 +191,11 @@ cover_def_32 (def_t *def, int *adj)
 	*adj = offset & 3;
 	if (offset & 3) {
 		if (def->alias) {
-			cover = alias_def (def->alias, def->type, def->offset);
+			cover = cover_alias_def (def->alias, def->type,
+									 def->offset - (offset & 3));
 		} else {
-			cover = alias_def (def, def->type, 0);
+			cover = cover_alias_def (def, def->type, -(offset & 3));
 		}
-		cover->offset -= offset & 3;
 	}
 	return cover;
 }
@@ -215,11 +215,11 @@ cover_def_64 (def_t *def, int *adj)
 	*adj = (offset & 6) >> 1;
 	if (offset & 6) {
 		if (def->alias) {
-			cover = alias_def (def->alias, def->type, def->offset);
+			cover = cover_alias_def (def->alias, def->type,
+									 def->offset - (offset & 6));
 		} else {
-			cover = alias_def (def, def->type, 0);
+			cover = cover_alias_def (def, def->type, -(offset & 6));
 		}
-		cover->offset -= offset & 6;
 	}
 	return cover;
 }