diff --git a/src/main/java/water/Key.java b/src/main/java/water/Key.java
index <HASH>..<HASH> 100644
--- a/src/main/java/water/Key.java
+++ b/src/main/java/water/Key.java
@@ -57,7 +57,7 @@ public final class Key extends Iced implements Comparable {
   public static final byte USER_KEY = 32;
 
   /** List of illegal characters which are not allowed in user keys. */
-  public static final CharSequence ILLEGAL_USER_KEY_CHARS = "!@#$%^&*()+={}[]|\\;:\"'<>,/?";
+  public static final CharSequence ILLEGAL_USER_KEY_CHARS = " !@#$%^&*()+={}[]|\\;:\"'<>,/?";
 
   // 64 bits of Cloud-specific cached stuff. It is changed atomically by any
   // thread that visits it and has the wrong Cloud. It has to be read *in the
Added ' ' into illegal user characters.