diff --git a/src/Mod/OpenSCAD/tokrules.py b/src/Mod/OpenSCAD/tokrules.py
index 75b3717573..c4360a1c31 100644
--- a/src/Mod/OpenSCAD/tokrules.py
+++ b/src/Mod/OpenSCAD/tokrules.py
@@ -86,7 +86,7 @@ tokens = reserved + (
 
 # Regular expression rules for simple tokens
 t_WORD    = r'[$]?[a-zA-Z_]+[0-9]*'
-t_NUMBER  = r'[-]?[0-9]*[\.]*[0-9]+([eE]-?[0-9]+)*'
+t_NUMBER  = r'[-]?[0-9]*[\.]*[0-9]+([eE][+-]?[0-9]+)*'
 t_LPAREN  = r'\('
 t_RPAREN  = r'\)'
 t_OBRACE  = r'{'