diff --git a/simpc-mode.el b/simpc-mode.el
index 928bb93..70fd4be 100644
--- a/simpc-mode.el
+++ b/simpc-mode.el
@@ -17,6 +17,10 @@
 
     (modify-syntax-entry ?& "." table)
     (modify-syntax-entry ?% "." table)
+
+    (modify-syntax-entry ?+ "." table)
+    (modify-syntax-entry ?- "." table)
+
     table))
 
 (defun simpc-types ()