diff --git a/source/src/command.cpp b/source/src/command.cpp
index 561a7251..c2fb9261 100644
--- a/source/src/command.cpp
+++ b/source/src/command.cpp
@@ -249,7 +249,7 @@ char *executeret(const char *p)                            // all evaluation hap
         ident *id = idents->access(c);
         if(!id)
         {
-            if(!isdigit(*c) && ((*c!='+' && *c!='-') || !isdigit(c[1]))) conoutf("unknown command: %s", c);
+            if(!isdigit(*c) && ((*c!='+' && *c!='-') || (*c && !isdigit(c[1])))) conoutf("unknown command: %s", c);
             setretval(newstring(c));
         }
         else