diff --git a/eustia/viewportScale.js b/eustia/viewportScale.js
index dc602e1..d386a37 100644
--- a/eustia/viewportScale.js
+++ b/eustia/viewportScale.js
@@ -5,7 +5,7 @@
  * ```
  */
 
-_('meta clamp trim each map');
+_('meta clamp trim each map isNaN');
 
 function exports() 
 {
@@ -31,5 +31,10 @@ function exports()
         if (key === 'minimum-scale') minScale = +val;
     });
 
-    return clamp(initialScale, minScale, maxScale);
+    let ret = clamp(initialScale, minScale, maxScale);
+
+    // Some will use ';' to be the separator, need to avoid the wrong result.
+    if (isNaN(ret)) return 1;
+
+    return ret;
 }
\ No newline at end of file
diff --git a/src/lib/util.js b/src/lib/util.js
index 3d4cb3b..eda1b00 100644
--- a/src/lib/util.js
+++ b/src/lib/util.js
@@ -6829,7 +6829,7 @@ export var viewportScale = _.viewportScale = (function ()
      */
 
     /* dependencies
-     * meta clamp trim each map 
+     * meta clamp trim each map isNaN 
      */
 
     function exports() 
@@ -6856,7 +6856,12 @@ export var viewportScale = _.viewportScale = (function ()
             if (key === 'minimum-scale') minScale = +val;
         });
 
-        return clamp(initialScale, minScale, maxScale);
+        let ret = clamp(initialScale, minScale, maxScale);
+
+        // Some will use ';' to be the separator, need to avoid the wrong result.
+        if (isNaN(ret)) return 1;
+
+        return ret;
     }
 
     return exports;