diff --git a/src/nimblepkg/options.nim b/src/nimblepkg/options.nim
index b1591b0..725b5ba 100644
--- a/src/nimblepkg/options.nim
+++ b/src/nimblepkg/options.nim
@@ -253,9 +253,10 @@ proc parseArgument*(key: string, result: var Options) =
     # Parse pkg@verRange
     if '@' in key:
       let i = find(key, '@')
-      let pkgTup = (key[0 .. i-1],
-        key[i+1 .. key.len-1].parseVersionRange())
-      result.action.packages.add(pkgTup)
+      let (pkgName, pkgVer) = (key[0 .. i-1], key[i+1 .. key.len-1])
+      if pkgVer.len == 0:
+        raise newException(NimbleError, "Version range expected after '@'.")
+      result.action.packages.add((pkgName, pkgVer.parseVersionRange()))
     else:
       result.action.packages.add((key, VersionRange(kind: verAny)))
   of actionRefresh: