diff --git a/src/CLI.cpp b/src/CLI.cpp
index 6d0ea5cc6..b0740ff68 100644
--- a/src/CLI.cpp
+++ b/src/CLI.cpp
@@ -28,6 +28,7 @@
 #include <sstream>
 #include <algorithm>
 #include <iostream> // TODO Remove.
+#include <ctype.h>
 #include <Context.h>
 #include <Nibbler.h>
 #include <Lexer.h>
@@ -2065,10 +2066,15 @@ bool CLI::isCommand (const std::string& raw) const
 }
 
 ////////////////////////////////////////////////////////////////////////////////
+// Valid tag
+//   - Length > 1
+//   - Starts with +/-
+//   - Tag does not start with a digit
 bool CLI::isTag (const std::string& raw) const
 {
   if (raw.size () >= 2                 &&
       (raw[0] == '+' || raw[0] == '-') &&
+      ! isdigit(raw[1])                &&
       raw.find (' ') == std::string::npos)
     return true;