diff --git a/common/membuf.c b/common/membuf.c
index 009fbc336..60491b590 100644
--- a/common/membuf.c
+++ b/common/membuf.c
@@ -231,3 +231,15 @@ peek_membuf (membuf_t *mb, size_t *len)
     *len = mb->len;
   return p;
 }
+
+/* To assist using membuf with function returning an error, this
+ * function sets the membuf into the error state.  */
+void
+set_membuf_err (membuf_t *mb, gpg_error_t err)
+{
+  if (!mb->out_of_core)
+    {
+      int myerr = gpg_err_code_to_errno (gpg_err_code (err));
+      mb->out_of_core = myerr? myerr : EINVAL;
+    }
+}
diff --git a/common/membuf.h b/common/membuf.h
index 1497bcd04..4b2be1a71 100644
--- a/common/membuf.h
+++ b/common/membuf.h
@@ -60,5 +60,6 @@ void put_membuf_printf (membuf_t *mb, const char *format,
 void *get_membuf (membuf_t *mb, size_t *len);
 void *get_membuf_shrink (membuf_t *mb, size_t *len);
 const void *peek_membuf (membuf_t *mb, size_t *len);
+void set_membuf_err (membuf_t *mb, gpg_error_t err);
 
 #endif /*GNUPG_COMMON_MEMBUF_H*/