diff --git a/src/db/ModelQuery.ts b/src/db/ModelQuery.ts
index 0708c02..b67f1d1 100644
--- a/src/db/ModelQuery.ts
+++ b/src/db/ModelQuery.ts
@@ -263,7 +263,7 @@ class FieldValue {
     }
 
     public toString(first: boolean = true): string {
-        return `${!first ? ',' : ''}${this.field}${this.test}${this.raw || this.value instanceof ModelQuery ? this.value : (Array.isArray(this.value) ? '(?)' : '?')}`;
+        return `${!first ? ',' : ''}${this.field}${this.test}${this.raw || this.value === null || this.value instanceof ModelQuery ? this.value : (Array.isArray(this.value) ? '(?)' : '?')}`;
     }
 
     protected get test(): string {
@@ -299,6 +299,13 @@ class WhereFieldValue extends FieldValue {
     }
 
     protected get test(): string {
+        if (this.value === null) {
+            if (this._test === WhereTest.EQ) {
+                return ' IS ';
+            } else if (this._test === WhereTest.NE) {
+                return ' IS NOT ';
+            }
+        }
         return this._test;
     }
 }
\ No newline at end of file