diff --git a/src/hb-ot-layout-gpos-table.hh b/src/hb-ot-layout-gpos-table.hh
index bda6f02b8..172a76458 100644
--- a/src/hb-ot-layout-gpos-table.hh
+++ b/src/hb-ot-layout-gpos-table.hh
@@ -706,7 +706,7 @@ struct MarkArray : Array16Of<MarkRecord>	/* Array of MarkRecords--in Coverage or
 
     float mark_x, mark_y, base_x, base_y;
 
-    buffer->unsafe_to_break (glyph_pos, buffer->idx);
+    buffer->unsafe_to_break (glyph_pos, buffer->idx + 1);
     mark_anchor.get_anchor (c, buffer->cur().codepoint, &mark_x, &mark_y);
     glyph_anchor.get_anchor (c, buffer->info[glyph_pos].codepoint, &base_x, &base_y);
 
diff --git a/test/shape/data/aots/tests/gpos4_simple.tests b/test/shape/data/aots/tests/gpos4_simple.tests
index d63829674..37a63f07c 100644
--- a/test/shape/data/aots/tests/gpos4_simple.tests
+++ b/test/shape/data/aots/tests/gpos4_simple.tests
@@ -1,4 +1,4 @@
-#../fonts/gpos4_simple_1.otf;--features="test" --single-par --no-clusters --no-glyph-names --ned;U+0011,U+0012,U+0013,U+0011;[17|18@1500,0|19@1400,-80|17@3000,0]
+../fonts/gpos4_simple_1.otf;--features="test" --single-par --no-clusters --no-glyph-names --ned;U+0011,U+0012,U+0013,U+0011;[17|18@1500,0|19@1400,-80|17@3000,0]
 ../fonts/gpos4_simple_1.otf;--features="test" --single-par --no-clusters --no-glyph-names --ned;U+0011,U+0011,U+0013,U+0011;[17|17@1500,0|19@3000,0|17@3000,0]
 ../fonts/gpos4_simple_1.otf;--features="test" --single-par --no-clusters --no-glyph-names --ned;U+0019,U+0019,U+0013,U+0011;[25|25@1500,0|19@3000,0|17@3000,0]
 #../fonts/gpos4_simple_1.otf;--features="test" --single-par --no-clusters --no-glyph-names --ned;U+0011,U+0012,U+0013,U+0013,U+0011;[17|18@1500,0|19@1400,-80|19@-100,-80|17@3000,0]
diff --git a/test/shape/data/aots/tests/gpos5.tests b/test/shape/data/aots/tests/gpos5.tests
index 6b6156139..85909545c 100644
--- a/test/shape/data/aots/tests/gpos5.tests
+++ b/test/shape/data/aots/tests/gpos5.tests
@@ -1,2 +1,2 @@
 ../fonts/gpos5_font1.otf;--features="test" --single-par --no-clusters --no-glyph-names --ned;U+0011,U+001E,U+0013,U+001F,U+0011;[17|18@1500,0|19@1400,-80|17@3000,0]
-#../fonts/gpos5_font1.otf;--features="test" --single-par --no-clusters --no-glyph-names --ned;U+0011,U+001E,U+001F,U+0013,U+0011;[17|18@1500,0|19@1401,-79|17@3000,0]
+../fonts/gpos5_font1.otf;--features="test" --single-par --no-clusters --no-glyph-names --ned;U+0011,U+001E,U+001F,U+0013,U+0011;[17|18@1500,0|19@1401,-79|17@3000,0]