diff --git a/ChangeLog b/ChangeLog
index 9d00e50e..b4bee120 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -13,6 +13,7 @@
 - fix gir build with g-o-i 1.66+ [László]
 - improve seek behaviour on pipes
 - add "speed" param to heifsave [lovell]
+- fix regression in C path for dilate / erode [kleisauke]
 
 9/8/20 started 8.10.1
 - fix markdown -> xml conversion in doc generation
diff --git a/libvips/morphology/morph.c b/libvips/morphology/morph.c
index 7f7ffc48..3e7fdb26 100644
--- a/libvips/morphology/morph.c
+++ b/libvips/morphology/morph.c
@@ -411,7 +411,6 @@ vips_dilate_gen( VipsRegion *or,
 	VipsMorph *morph = (VipsMorph *) b;
 	VipsImage *M = morph->M;
 	VipsRegion *ir = seq->ir;
-	int * restrict t = morph->coeff;
 
 	int *soff = seq->soff;
 	int *coff = seq->coff;
@@ -424,6 +423,7 @@ vips_dilate_gen( VipsRegion *or,
 
 	VipsRect s;
 	int x, y;
+	int *t;
 	int result, i;
 
 	/* Prepare the section of the input image we need. A little larger
@@ -448,9 +448,9 @@ vips_dilate_gen( VipsRegion *or,
 
 		seq->ss = 0;
 		seq->cs = 0;
-		for( y = 0; y < M->Ysize; y++ )
-			for( x = 0; x < M->Xsize; x++ )
-				switch( t[x] ) {
+		for( t = morph->coeff, y = 0; y < M->Ysize; y++ )
+			for( x = 0; x < M->Xsize; x++, t++ )
+				switch( *t ) {
 				case 255:
 					soff[seq->ss++] =
 						VIPS_REGION_ADDR( ir, 
@@ -522,7 +522,6 @@ vips_erode_gen( VipsRegion *or,
 	VipsMorph *morph = (VipsMorph *) b;
 	VipsImage *M = morph->M;
 	VipsRegion *ir = seq->ir;
-	int * restrict t = morph->coeff;
 
 	int *soff = seq->soff;
 	int *coff = seq->coff;
@@ -535,6 +534,7 @@ vips_erode_gen( VipsRegion *or,
 
 	VipsRect s;
 	int x, y;
+	int *t;
 	int result, i;
 
 	/* Prepare the section of the input image we need. A little larger
@@ -559,9 +559,9 @@ vips_erode_gen( VipsRegion *or,
 
 		seq->ss = 0;
 		seq->cs = 0;
-		for( y = 0; y < M->Ysize; y++ )
-			for( x = 0; x < M->Xsize; x++ )
-				switch( t[x] ) {
+		for( t = morph->coeff, y = 0; y < M->Ysize; y++ )
+			for( x = 0; x < M->Xsize; x++, t++ )
+				switch( *t ) {
 				case 255:
 					soff[seq->ss++] =
 						VIPS_REGION_ADDR( ir,