diff --git a/ChangeLog b/ChangeLog
index 00def3157..eab381a0c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2018-06-16  Werner Lemberg  <wl@gnu.org>
+
+	* src/base/ftbitmap.c (FT_Bitmap_Blend): Avoid integer overflow.
+
 2018-06-16  Werner Lemberg  <wl@gnu.org>
 
 	Add `FT_Bitmap_Blend' API.
diff --git a/src/base/ftbitmap.c b/src/base/ftbitmap.c
index e848e66a3..be36dbd29 100644
--- a/src/base/ftbitmap.c
+++ b/src/base/ftbitmap.c
@@ -901,8 +901,11 @@
     source_llx -= final_llx;
     source_lly -= final_lly;
 
-    target_llx -= final_llx;
-    target_lly -= final_lly;
+    if ( target->width && target->rows )
+    {
+      target_llx -= final_llx;
+      target_lly -= final_lly;
+    }
 
     /* set up target bitmap */
     if ( target->pixel_mode == FT_PIXEL_MODE_NONE )