diff --git a/libvips/morphology/hitmiss.c b/libvips/morphology/hitmiss.c
index 0abbe60e..093b5ea4 100644
--- a/libvips/morphology/hitmiss.c
+++ b/libvips/morphology/hitmiss.c
@@ -738,10 +738,7 @@ morphology( IMAGE *in, IMAGE *out, INTMASK *mask, MorphOp op )
 	else
 		generate = erode_gen;
 
-	/* Set demand hints. FATSTRIP is good for us, as THINSTRIP will cause
-	 * too many recalculations on overlaps.
-	 */
-	if( im_demand_hint( morph->out, IM_FATSTRIP, morph->in, NULL ) ||
+	if( im_demand_hint( morph->out, IM_SMALLTILE, morph->in, NULL ) ||
 		im_generate( morph->out, 
 			morph_start, generate, morph_stop, morph->in, morph ) )
 		return( -1 );
diff --git a/libvips/morphology/im_rank.c b/libvips/morphology/im_rank.c
index 915dba1d..1e4c2484 100644
--- a/libvips/morphology/im_rank.c
+++ b/libvips/morphology/im_rank.c
@@ -367,10 +367,7 @@ im_rank_raw( IMAGE *in, IMAGE *out, int xsize, int ysize, int index )
 		return( -1 );
 	}
 
-	/* Set demand hints. FATSTRIP is good for us, as THINSTRIP will cause
-	 * too many recalculations on overlaps.
-	 */
-	if( im_demand_hint( out, IM_FATSTRIP, in, NULL ) )
+	if( im_demand_hint( out, IM_SMALLTILE, in, NULL ) )
 		return( -1 );
 
 	/* Generate!