diff --git a/src/diff.c b/src/diff.c
index c348894..41d61b1 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -2351,7 +2351,8 @@
     // Don't run linematch when lnum is offscreen.  Useful for scrollbind
     // calculations which need to count all the filler lines above the screen.
     if (lnum >= wp->w_topline && lnum < wp->w_botline
-				&& !dp->is_linematched && diff_linematch(dp))
+				&& !dp->is_linematched && diff_linematch(dp)
+				&& diff_check_sanity(curtab, dp))
       run_linematch_algorithm(dp);
 
     if (dp->is_linematched)
diff --git a/src/testdir/dumps/Test_linematch_3diffs2.dump b/src/testdir/dumps/Test_linematch_3diffs2.dump
new file mode 100644
index 0000000..3a333e6
--- /dev/null
+++ b/src/testdir/dumps/Test_linematch_3diffs2.dump
@@ -0,0 +1,20 @@
+| +0#0000e05#a8a8a8255@1|a+0#0000000#5fd7ff255|b|c|d|q| @17||+1&#ffffff0| +0#0000e05#a8a8a8255@1|-+0#4040ff13#afffff255@21||+1#0000000#ffffff0| +0#0000e05#a8a8a8255@1|-+0#4040ff13#afffff255@21
+| +0#0000e05#a8a8a8255@1|d+0#0000000#ffd7ff255|e|f| @19||+1&#ffffff0| +0#0000e05#a8a8a8255@1|d+0#0000000#ffd7ff255|e|f|q+2&#ff404010| +0&#ffd7ff255@17||+1&#ffffff0| +0#0000e05#a8a8a8255@1|-+0#4040ff13#afffff255@21
+| +0#0000e05#a8a8a8255@1|h+0#0000000#ffd7ff255|i|j|k|l+2&#ff404010|m| +0&#ffd7ff255@16||+1&#ffffff0| +0#0000e05#a8a8a8255@1|h+0#0000000#ffd7ff255|i|j|k| @17||+1&#ffffff0| +0#0000e05#a8a8a8255@1|h+0#0000000#ffd7ff255|i|j|k|l+2&#ff404010|m| +0&#ffd7ff255@15
+| +0#0000e05#a8a8a8255@1|-+0#4040ff13#afffff255@22||+1#0000000#ffffff0| +0#0000e05#a8a8a8255@1|n+0#0000000#ffd7ff255|o|p|q| @17||+1&#ffffff0| +0#0000e05#a8a8a8255@1|n+0#0000000#ffd7ff255|o|p|q|r+2&#ff404010| +0&#ffd7ff255@16
+| +0#0000e05#a8a8a8255@1> +0#0000000#ffd7ff255@22||+1&#ffffff0| +0#0000e05#a8a8a8255@1|-+0#4040ff13#afffff255@21||+1#0000000#ffffff0| +0#0000e05#a8a8a8255@1|s+2#0000000#ff404010|t|u|v| +0&#ffd7ff255@17
+|~+0#4040ff13#ffffff0| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|~| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|~| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|~| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|~| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|~| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|~| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|~| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|~| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|~| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|~| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|~| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|~| @23||+1#0000000&|~+0#4040ff13&| @22||+1#0000000&|~+0#4040ff13&| @22
+|<+3#0000000&|e|m|a|t|c|h|1| |[|+|]| |4|,|1| @5|A|l@1| |<+1&&|l|i|n|e|m|a|t|c|h|2| |3|,|1| @5|A|l@1| |<|l|i|n|e|m|a|t|c|h|3| |3|,|1| @5|A|l@1
+|-+2&&@1| |I|N|S|E|R|T| |-@1| +0&&@62
diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
index 8939bb8..36d3d9b 100644
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
Binary files differ
diff --git a/src/version.c b/src/version.c
index 46c4818..d6b73fd 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1027,
+/**/
     1026,
 /**/
     1025,