diff --git a/src/ftfont.c b/src/ftfont.c
index 4380a48d8dc..384279f616b 100644
--- a/src/ftfont.c
+++ b/src/ftfont.c
@@ -613,7 +613,7 @@ ftfont_get_open_type_spec (Lisp_Object otf_spec)
 	      unsigned int tag;
 
 	      OTF_SYM_TAG (XCAR (val), tag);
-	      spec->features[i][j++] = negative ? tag & 0x80000000 : tag;
+	      spec->features[i][j++] = negative ? tag | 0x80000000 : tag;
 	    }
 	}
       spec->nfeatures[i] = j;
diff --git a/src/macfont.m b/src/macfont.m
index abdf0ecfe59..f736fbf0e1e 100644
--- a/src/macfont.m
+++ b/src/macfont.m
@@ -1824,7 +1824,7 @@ macfont_get_open_type_spec (Lisp_Object otf_spec)
               unsigned int tag;
 
               OTF_SYM_TAG (XCAR (val), tag);
-              spec->features[i][j++] = negative ? tag & 0x80000000 : tag;
+              spec->features[i][j++] = negative ? tag | 0x80000000 : tag;
             }
         }
       spec->nfeatures[i] = j;