diff --git a/ChangeLog b/ChangeLog
index 5e8fe81e4..382683faf 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2018-07-27  Werner Lemberg  <wl@gnu.org>
+
+	[truetype] Make `TT_Set_MM_Blend' idempotent (#54388).
+
+	* src/truetype/ttgxvar.c (tt_set_mm_blend): Correctly set
+	`face->doblend' if the current call to the function yields the same
+	blend coordinates as the previous call.
+
 2018-07-27  Werner Lemberg  <wl@gnu.org>
 
 	[psaux, type1]: More tracing improvements.
diff --git a/src/truetype/ttgxvar.c b/src/truetype/ttgxvar.c
index d143fcefc..3df50d630 100644
--- a/src/truetype/ttgxvar.c
+++ b/src/truetype/ttgxvar.c
@@ -2555,7 +2555,11 @@
 
       /* return value -1 indicates `no change' */
       if ( !have_diff )
+      {
+        face->doblend = TRUE;
+
         return -1;
+      }
 
       for ( ; i < mmvar->num_axis; i++ )
       {