diff --git a/tools/qfcc/include/def.h b/tools/qfcc/include/def.h
index 5ff4b7afd..51da57204 100644
--- a/tools/qfcc/include/def.h
+++ b/tools/qfcc/include/def.h
@@ -119,13 +119,18 @@ def_t *new_def (const char *name, struct type_s *type,
 	Aliasing a def to the same type is useless, but not checked. Aliasing a
 	def to a type larger than the def's type will generate an internal error.
 
+	If the offset is negative, or the offset plus the size of the aliasing type
+	is greater than the size of the def's type, then an internal error will
+	be generated.
+
 	\param def		The def to be aliased.
 	\param type		The type of the alias.
+	\param offset	Offset of the alias relative to the def.
 	\return			The def aliasing \a def.
 
 	\todo Make aliasing to the same type a no-op?
 */
-def_t *alias_def (def_t *def, struct type_s *type);
+def_t *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 87d7a0388..864dc89fe 100644
--- a/tools/qfcc/source/def.c
+++ b/tools/qfcc/source/def.c
@@ -145,7 +145,7 @@ new_def (const char *name, type_t *type, defspace_t *space,
 }
 
 def_t *
-alias_def (def_t *def, type_t *type)
+alias_def (def_t *def, type_t *type, int offset)
 {
 	def_t      *alias;
 
@@ -157,9 +157,12 @@ alias_def (def_t *def, type_t *type)
 	}
 	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");
 	ALLOC (16384, def_t, defs, alias);
 	alias->return_addr = __builtin_return_address (0);
-	alias->offset = def->offset;
+	alias->offset = offset;
+	alias->offset_reloc = 1;
 	alias->type = type;
 	alias->alias = def;
 	alias->line = pr.source_line;
diff --git a/tools/qfcc/source/emit.c b/tools/qfcc/source/emit.c
index e0c9f074f..b0cf19de9 100644
--- a/tools/qfcc/source/emit.c
+++ b/tools/qfcc/source/emit.c
@@ -72,7 +72,7 @@ get_value_def (ex_value_t *value, etype_t type)
 	}
 	def = emit_value (value, 0);
 	if (type != def->type->type)
-		return alias_def (def, ev_types[type]);
+		return alias_def (def, ev_types[type], 0);
 	return def;
 }
 
@@ -89,7 +89,7 @@ get_operand_def (expr_t *expr, operand_t *op)
 				case sy_var:
 					if (op->type != op->o.symbol->type->type)
 						return alias_def (op->o.symbol->s.def,
-										  ev_types[op->type]);
+										  ev_types[op->type], 0);
 					return op->o.symbol->s.def;
 				case sy_func:
 					return op->o.symbol->s.func->def;
@@ -114,16 +114,15 @@ get_operand_def (expr_t *expr, operand_t *op)
 		case op_pointer:
 			def = op->o.value->v.pointer.def;
 			if (op->o.value->v.pointer.val || op->type != def->type->type) {
-				def = alias_def (def, ev_types[op->type]);
-				def->offset = op->o.value->v.pointer.val;
-				def->offset_reloc = 1;
+				def = alias_def (def, ev_types[op->type],
+								 op->o.value->v.pointer.val);
 			}
 			return def;
 		case op_alias:
 			def = get_operand_def (expr, op->o.alias);
 			if (def->alias)
 				def = def->alias;
-			def = alias_def (def, ev_types[op->type]);
+			def = alias_def (def, ev_types[op->type], 0);
 			return def;
 	}
 	return 0;