diff --git a/src/cairo-image-compositor.c b/src/cairo-image-compositor.c
index 79ad69f68..4f8aaed99 100644
--- a/src/cairo-image-compositor.c
+++ b/src/cairo-image-compositor.c
@@ -2610,14 +2610,14 @@ _inplace_src_spans (void *abstract_renderer, int y, int h,
 		    unsigned num_spans)
 {
     cairo_image_span_renderer_t *r = abstract_renderer;
-    uint8_t *m;
+    uint8_t *m, *base = (uint8_t*)pixman_image_get_data(r->mask);
     int x0;
 
     if (num_spans == 0)
 	return CAIRO_STATUS_SUCCESS;
 
     x0 = spans[0].x;
-    m = r->_buf;
+    m = base;
     do {
 	int len = spans[1].x - spans[0].x;
 	if (len >= r->u.composite.run_length && spans[0].coverage == 0xff) {
@@ -2655,7 +2655,7 @@ _inplace_src_spans (void *abstract_renderer, int y, int h,
 				      spans[0].x, y,
 				      spans[1].x - spans[0].x, h);
 
-	    m = r->_buf;
+	    m = base;
 	    x0 = spans[1].x;
 	} else if (spans[0].coverage == 0x0) {
 	    if (spans[0].x != x0) {
@@ -2684,7 +2684,7 @@ _inplace_src_spans (void *abstract_renderer, int y, int h,
 #endif
 	    }
 
-	    m = r->_buf;
+	    m = base;
 	    x0 = spans[1].x;
 	} else {
 	    *m++ = spans[0].coverage;
diff --git a/test/Makefile.sources b/test/Makefile.sources
index 7eb73647f..86494348d 100644
--- a/test/Makefile.sources
+++ b/test/Makefile.sources
@@ -34,6 +34,7 @@ test_sources = \
 	bug-source-cu.c					\
 	bug-extents.c					\
 	bug-seams.c					\
+	bug-image-compositor.c				\
 	caps.c						\
 	checkerboard.c					\
 	caps-joins.c					\
diff --git a/test/bug-image-compositor.c b/test/bug-image-compositor.c
new file mode 100644
index 000000000..304ea089c
--- /dev/null
+++ b/test/bug-image-compositor.c
@@ -0,0 +1,66 @@
+/*
+ * Copyright © 2020 Uli Schlachter, Heiko Lewin
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * Author: Uli Schlachter <psychon@znc.in>
+ * Author: Heiko Lewin <hlewin@gmx.de>
+ */
+#include "cairo-test.h"
+
+
+/* This test reproduces an overflow of a mask-buffer in cairo-image-compositor.c */
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    cairo_set_source_rgb (cr, 0., 0., 0.);
+    cairo_paint (cr);
+
+    cairo_set_source_rgb (cr, 1., 1., 1.);
+    cairo_set_line_width (cr, 1.);
+
+    cairo_pattern_t *p = cairo_pattern_create_linear (0, 0, width, height);
+    cairo_pattern_add_color_stop_rgb (p, 0, 0.99, 1, 1);
+    cairo_pattern_add_color_stop_rgb (p, 1, 1, 1, 1);
+    cairo_set_source (cr, p);
+    cairo_pattern_destroy(p);
+
+    cairo_move_to (cr, 0.5, -1);
+    for (int i = 0; i < width; i+=3) {
+	cairo_rel_line_to (cr, 2, 2);
+	cairo_rel_line_to (cr, 1, -2);
+    }
+
+    cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
+    cairo_stroke (cr);
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+
+CAIRO_TEST (bug_image_compositor,
+	    "Crash in image-compositor",
+	    "stroke, stress", /* keywords */
+	    NULL, /* requirements */
+	    10000, 1,
+	    NULL, draw)
+	    
diff --git a/test/meson.build b/test/meson.build
index 0e2e23673..b8149a7bc 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -32,6 +32,7 @@ test_sources = [
   'bug-bo-ricotz.c',
   'bug-source-cu.c',
   'bug-extents.c',
+  'bug-image-compositor.c',  
   'bug-seams.c',
   'caps.c',
   'checkerboard.c',
diff --git a/test/reference/bug-image-compositor.ref.png b/test/reference/bug-image-compositor.ref.png
new file mode 100644
index 000000000..939f659d2
Binary files /dev/null and b/test/reference/bug-image-compositor.ref.png differ