diff --git a/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/IntroduceStaticTypeCastRule.java b/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/IntroduceStaticTypeCastRule.java
index 6597b44..b91abe7 100644
--- a/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/IntroduceStaticTypeCastRule.java
+++ b/asterix-algebra/src/main/java/edu/uci/ics/asterix/optimizer/rules/IntroduceStaticTypeCastRule.java
@@ -295,7 +295,7 @@
             }
             // the input has extra fields
             if (!matched && !reqType.isOpen())
-                throw new AlgebricksException("static type mismatch: including an extra closed field" + fieldName);
+                throw new AlgebricksException("static type mismatch: including an extra closed field "  + fieldName);
         }
 
         // backward match: match from required to actual
@@ -338,7 +338,7 @@
                 nullFields[i] = true;
             } else {
                 // no matched field in the input for a required closed field
-                throw new AlgebricksException("static type mismatch: miss a required closed field" + reqFieldName);
+                throw new AlgebricksException("static type mismatch: miss a required closed field " + reqFieldName);
             }
         }