diff --git a/app/base/temp-buf.c b/app/base/temp-buf.c
index 3cab8052c1..61fc650155 100644
--- a/app/base/temp-buf.c
+++ b/app/base/temp-buf.c
@@ -352,7 +352,7 @@ temp_buf_free (TempBuf *buf)
 }
 
 guchar *
-temp_buf_get_data (TempBuf *buf)
+temp_buf_get_data (const TempBuf *buf)
 {
   return buf->data;
 }
diff --git a/app/base/temp-buf.h b/app/base/temp-buf.h
index c4f33c589e..fd31fe598f 100644
--- a/app/base/temp-buf.h
+++ b/app/base/temp-buf.h
@@ -61,7 +61,7 @@ TempBuf * temp_buf_copy_area     (TempBuf       *src,
 void      temp_buf_demultiply    (TempBuf       *buf);
 
 void      temp_buf_free          (TempBuf       *buf);
-guchar  * temp_buf_get_data      (TempBuf       *buf);
+guchar  * temp_buf_get_data      (const TempBuf *buf);
 gsize     temp_buf_get_data_size (TempBuf       *buf);
 guchar  * temp_buf_data_clear    (TempBuf       *buf);