debian/changelog

+qgis (2.18.20+dfsg-2) unstable; urgency=medium
+
+  * Bump minimum GRASS build dependency version to 7.4.1.
+
+ -- Bas Couwenberg <sebastic@debian.org>  Tue, 12 Jun 2018 23:16:07 +0200
+
 qgis (2.18.20+dfsg-1) unstable; urgency=medium
 
   * Update symbols for other architectures.

debian/control

@@ -10,7 +10,7 @@ Build-Depends: bison,
                dh-python,
                flex,
                gdal-bin,
-               grass-dev (>= 7.4.0),
+               grass-dev (>= 7.4.1),
                libexpat1-dev,
                libfcgi-dev,
                libgdal-dev (>= 1.10.1-0~),