diff --git a/lib/Builders/MySqlClauseBuilder.php b/lib/Builders/MySqlClauseBuilder.php
index c19a47a..9dd45a9 100644
--- a/lib/Builders/MySqlClauseBuilder.php
+++ b/lib/Builders/MySqlClauseBuilder.php
@@ -125,10 +125,17 @@ protected function addCondition($field, string $operator, array $values, ?string
             return $this;
         }
 
-        $placeholder = $this->generatePlaceholder($field, $values, $operator);
-
         $fieldStr = $this->getFieldString($field);
 
+        // If the field isn't on the active table, drop the whole predicate.
+        // Otherwise we'd push `null` for the field but still emit the operator
+        // and placeholder, producing invalid SQL like `WHERE = 'value'`.
+        if ($fieldStr === null) {
+            return $this;
+        }
+
+        $placeholder = $this->generatePlaceholder($field, $values, $operator);
+
         if (!empty($this->clauses) && $logic && in_array(strtoupper($logic), ['AND', 'OR'])) {
             $this->clauses[] = strtoupper($logic);
         }