diff --git a/ChangeLog b/ChangeLog
index d93f1feb7..fbeba5e0f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -164,6 +164,7 @@
 - TW-1701 Some generated UUIDs deemed invalid (thanks to Wim Schuermann).
 - TW-1707 Context can leak into modifications (thanks to Tomas Babej).
 - TW-1715 Dates misinterpreted when no dateformat active.
+- TW-1716 on-modify hooks fail if `date.iso` is not set (thanks to Jens Erat).
 - Prevent potential task duplication during import for non-pending tasks.
 - Show the active context in "context list", if any is active.
 - Fix "task edit" dropping annotation text after newlines.
diff --git a/src/ISO8601.cpp b/src/ISO8601.cpp
index d420b0aef..e1b1c82ce 100644
--- a/src/ISO8601.cpp
+++ b/src/ISO8601.cpp
@@ -247,13 +247,18 @@ bool ISO8601d::parse (
     }
   }
 
-  else if (ISO8601d::isoEnabled &&
-           (parse_date_time     (n)   || // Strictest first.
-            parse_date_time_ext (n)   ||
-            parse_date_ext      (n)   ||
-            parse_time_utc_ext  (n)   ||
-            parse_time_off_ext  (n)   ||
-            parse_time_ext      (n)))    // Time last, as it is the most permissive.
+  // Allow parse_date_time and parse_date_time_ext regardless of
+  // ISO8601d::isoEnabled setting, because these formats are relied upon by
+  // the 'import' command, JSON parser and hook system.
+  else if (parse_date_time     (n)   || // Strictest first.
+           parse_date_time_ext (n)   ||
+           (ISO8601d::isoEnabled &&
+            (parse_date_time     (n) ||
+             parse_date_time_ext (n) ||
+             parse_date_ext      (n) ||
+             parse_time_utc_ext  (n) ||
+             parse_time_off_ext  (n) ||
+             parse_time_ext      (n)))) // Time last, as it is the most permissive.
   {
     // Check the values and determine time_t.
     if (validate ())
diff --git a/test/import.t b/test/import.t
index 4431dea7e..3d3bc02b6 100755
--- a/test/import.t
+++ b/test/import.t
@@ -302,6 +302,23 @@ class TestImportValidate(TestCase):
         self.assertIn("The status 'foo' is not valid.", err)
 
 
+class TestImportWithoutISO(TestCase):
+    def setUp(self):
+        self.t = Task()
+
+    def test_import_with_iso_enabled(self):
+        j = '{"uuid":"a2a2a2a2-a2a2-a2a2-a2a2-a2a2a2a2a2a2", "description":"one", "entry":"20151018T144200"}'
+        self.t("import rc.date.iso=1", input=j)
+        code, out, err = self.t("_get 1.entry")
+        self.assertIn("2015-10-18T14:42:00\n", out)
+
+    def test_import_with_iso_disabled(self):
+        j = '{"uuid":"a2a2a2a2-a2a2-a2a2-a2a2-a2a2a2a2a2a2", "description":"one", "entry":"20151018T144200"}'
+        self.t("import rc.date.iso=0", input=j)
+        code, out, err = self.t("_get 1.entry")
+        self.assertIn("2015-10-18T14:42:00\n", out)
+
+
 if __name__ == "__main__":
     from simpletap import TAPTestRunner
     unittest.main(testRunner=TAPTestRunner())