diff --git a/ext/sqlite3/database.c b/ext/sqlite3/database.c
index 36b75787..884b37be 100644
--- a/ext/sqlite3/database.c
+++ b/ext/sqlite3/database.c
@@ -277,32 +277,34 @@ last_insert_row_id(VALUE self)
 VALUE
 sqlite3val2rb(sqlite3_value *val)
 {
+    VALUE rb_val;
+
     switch (sqlite3_value_type(val)) {
         case SQLITE_INTEGER:
-            return LL2NUM(sqlite3_value_int64(val));
+            rb_val = LL2NUM(sqlite3_value_int64(val));
             break;
         case SQLITE_FLOAT:
-            return rb_float_new(sqlite3_value_double(val));
+            rb_val = rb_float_new(sqlite3_value_double(val));
             break;
-        case SQLITE_TEXT:
-            return rb_str_new2((const char *)sqlite3_value_text(val));
+        case SQLITE_TEXT: {
+            rb_val = rb_utf8_str_new_cstr((const char *)sqlite3_value_text(val));
+            rb_obj_freeze(rb_val);
             break;
+        }
         case SQLITE_BLOB: {
-            /* Sqlite warns calling sqlite3_value_bytes may invalidate pointer from sqlite3_value_blob,
-               so we explicitly get the length before getting blob pointer.
-               Note that rb_str_new apparently create string with ASCII-8BIT (BINARY) encoding,
-               which is what we want, as blobs are binary
-             */
             int len = sqlite3_value_bytes(val);
-            return rb_str_new((const char *)sqlite3_value_blob(val), len);
+            rb_val = rb_str_new((const char *)sqlite3_value_blob(val), len);
+            rb_obj_freeze(rb_val);
             break;
         }
         case SQLITE_NULL:
-            return Qnil;
+            rb_val = Qnil;
             break;
         default:
-            rb_raise(rb_eRuntimeError, "bad type"); /* FIXME */
+            rb_raise(rb_eRuntimeError, "bad type");
     }
+
+    return rb_val;
 }
 
 void
diff --git a/test/test_database.rb b/test/test_database.rb
index 04f226cd..ef43636a 100644
--- a/test/test_database.rb
+++ b/test/test_database.rb
@@ -15,6 +15,36 @@ def teardown
       @db.close unless @db.closed?
     end
 
+    def test_custom_function_encoding
+      @db.execute("CREATE TABLE
+                       sourceTable(
+                         sourceData TEXT);")
+      @db.execute("INSERT INTO sourceTable
+                     VALUES ('abcde');")
+
+      @db.create_function("GetCopy", 1) { |func, value|
+        func.result = value
+      }
+
+      @db.transaction { |t|
+        t.execute("CREATE TABLE
+                         afterTable(
+                           beforeData TEXT,
+                           afterData TEXT);".squeeze(" "))
+
+        t.execute("INSERT INTO afterTable
+                       SELECT
+                         sourceData,
+                         GetCopy(sourceData)
+                       FROM sourceTable;")
+      }
+
+      assert_equal(1, @db.get_first_value("SELECT 1
+                                        FROM afterTable
+                                        WHERE beforeData = afterData
+                                        LIMIT 1;"))
+    end
+
     def test_segv
       assert_raises { SQLite3::Database.new 1 } # rubocop:disable Minitest/UnspecifiedException
     end