diff --git a/src/backends/gr.jl b/src/backends/gr.jl
index e28fb2d8..8fb040ea 100644
--- a/src/backends/gr.jl
+++ b/src/backends/gr.jl
@@ -27,7 +27,7 @@ gr_markertype(k) = (
     octagon = -24,
     cross = 2,
     xcross = 5,
-    + = 2,
+    (+) = 2,
     x = 5,
     star4 = -25,
     star5 = -26,
diff --git a/src/backends/pgfplotsx.jl b/src/backends/pgfplotsx.jl
index 030ddefa..cde7fd9b 100644
--- a/src/backends/pgfplotsx.jl
+++ b/src/backends/pgfplotsx.jl
@@ -708,7 +708,7 @@ pgfx_get_marker(k) = get(
         none = "none",
         cross = "+",
         xcross = "x",
-        + = "+",
+        (+) = "+",
         x = "x",
         utriangle = "triangle*",
         dtriangle = "triangle*",