diff --git a/c/c.go b/c/c.go
index dd99c52..8d6a3ea 100644
--- a/c/c.go
+++ b/c/c.go
@@ -52,6 +52,7 @@ type integer interface {
 
 type SizeT = uintptr
 type SsizeT = Long
+type PtrdiffT = Long
 
 type IntptrT = uintptr
 type UintptrT = uintptr
diff --git a/c/llcppg.pub b/c/llcppg.pub
index d40e7f5..e97dbb1 100644
--- a/c/llcppg.pub
+++ b/c/llcppg.pub
@@ -3,6 +3,7 @@ D github.com/goplus/lib/c/time
 T FILE FILE
 T size_t SizeT
 T ssize_t SsizeT
+T ptrdiff_t PtrdiffT
 T intptr_t IntptrT
 T uintptr_t UintptrT
 T int8_t Int8T