diff --git a/ChangeLog b/ChangeLog
index 8faab78a..4a67d11f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2008-11-18  Andreas Rottmann  <a.rottmann@gmx.at>
+
+	* girepository/girnode.c (g_ir_node_build_typelib): Use sizeof()
+	instead of hard-coding struct sizes.
+
 2008-11-18  Owen Taylor <otaylor@redhat.com>
 
 	Bug 561296 - Add "storage type" to the typelib data for enums
diff --git a/girepository/girnode.c b/girepository/girnode.c
index 8e9d5d1a..75dd265c 100644
--- a/girepository/girnode.c
+++ b/girepository/girnode.c
@@ -1576,8 +1576,8 @@ g_ir_node_build_typelib (GIrNode    *node,
 	signature = *offset2;
 	n = g_list_length (function->parameters);
 
-	*offset += 16;
-	*offset2 += 8 + n * 12;
+	*offset += sizeof(FunctionBlob);
+	*offset2 += sizeof(SignatureBlob) + n * sizeof(ArgBlob);
 
 	blob->blob_type = BLOB_TYPE_FUNCTION;
 	blob->deprecated = function->deprecated;
@@ -1628,8 +1628,8 @@ g_ir_node_build_typelib (GIrNode    *node,
 	signature = *offset2;
 	n = g_list_length (function->parameters);
 
-	*offset += 12;
-	*offset2 += 8 + n * 12;
+	*offset += sizeof(CallbackBlob);
+	*offset2 += sizeof(SignatureBlob) + n * sizeof(ArgBlob);
 
 	blob->blob_type = BLOB_TYPE_CALLBACK;
 	blob->deprecated = function->deprecated;
@@ -1671,8 +1671,8 @@ g_ir_node_build_typelib (GIrNode    *node,
 	signature = *offset2;
 	n = g_list_length (signal->parameters);
 
-	*offset += 12;
-	*offset2 += 8 + n * 12;
+	*offset += sizeof(SignalBlob);
+	*offset2 += sizeof(SignatureBlob) + n * sizeof(ArgBlob);
 
 	blob->deprecated = signal->deprecated;
 	blob->run_first = signal->run_first;
@@ -1722,8 +1722,8 @@ g_ir_node_build_typelib (GIrNode    *node,
 	signature = *offset2;
 	n = g_list_length (vfunc->parameters);
 
-	*offset += 16;
-	*offset2 += 8 + n * 12;
+	*offset += sizeof(VFuncBlob);
+	*offset2 += sizeof(SignatureBlob) + n * sizeof(ArgBlob);
 
 	blob->name = write_string (node->name, strings, data, offset2);
 	blob->must_chain_up = 0; /* FIXME */