diff --git a/jOOQ/src/main/java/org/jooq/impl/Val.java b/jOOQ/src/main/java/org/jooq/impl/Val.java
index 40fc577773..0821af4305 100644
--- a/jOOQ/src/main/java/org/jooq/impl/Val.java
+++ b/jOOQ/src/main/java/org/jooq/impl/Val.java
@@ -257,6 +257,12 @@ class Val<T> extends AbstractParam<T> {
             toSQL(context, value, getConverter());
         }
 
+        // [#1727] VARCHAR types should be cast to their actual lengths in some
+        // dialects
+        else if ((type == SQLDataType.VARCHAR || type == SQLDataType.CHAR) && asList(FIREBIRD).contains(family)) {
+            toSQLCast(context, dataType, getValueLength(), 0, 0);
+        }
+
         /* [pro] xx
         xx xxxxxxx xxxx xxxx xxxxx xxxxxx xxx xx xxxx xx xxx xxxxxx xx xxxx xxxxxxxx
         xxxx xx xxxxx xx xxxxxxxxxxxxxxxxxxxxxxx xx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx x
@@ -270,6 +276,28 @@ class Val<T> extends AbstractParam<T> {
         }
     }
 
+    private final int getValueLength() {
+        String string = (String) value;
+        if (string == null) {
+            return 1;
+        }
+
+        else {
+            int length = string.length();
+
+            // If non 7-bit ASCII characters are present, multiply the length by
+            // 4 to be sure that even UTF-32 collations will fit. But don't use
+            // larger numbers than Derby's upper limit 32672
+            for (int i = 0; i < length; i++) {
+                if (string.charAt(i) > 127) {
+                    return Math.min(32672, 4 * length);
+                }
+            }
+
+            return Math.min(32672, length);
+        }
+    }
+
     private final void toSQLCast(RenderContext context, DataType<?> type, int length, int precision, int scale) {
         context.keyword("cast").sql("(");
         toSQL(context, value, getConverter());