diff --git a/t/t9011-svn-da.sh b/t/t9011-svn-da.sh
index be1234094f..90b6058ab6 100755
--- a/t/t9011-svn-da.sh
+++ b/t/t9011-svn-da.sh
@@ -86,4 +86,39 @@ test_expect_success 'nonempty (but unused) preimage view' '
 	test_cmp empty actual
 '
 
+test_expect_success 'preimage view: right endpoint cannot backtrack' '
+	printf "SVNQ%b%b" "Q\003QQQ" "Q\002QQQ" |
+		q_to_nul >clear.backtrack &&
+	test_must_fail test-svn-fe -d preimage clear.backtrack 14
+'
+
+test_expect_success 'preimage view: left endpoint can advance' '
+	printf "SVNQ%b%b" "Q\003QQQ" "\001\002QQQ" |
+		q_to_nul >clear.preshrink &&
+	printf "SVNQ%b%b" "Q\003QQQ" "\001\001QQQ" |
+		q_to_nul >clear.shrinkbacktrack &&
+	test-svn-fe -d preimage clear.preshrink 14 >actual &&
+	test_must_fail test-svn-fe -d preimage clear.shrinkbacktrack 14 &&
+	test_cmp empty actual
+'
+
+test_expect_success 'preimage view: offsets compared by value' '
+	printf "SVNQ%b%b" "\001\001QQQ" "\0200Q\003QQQ" |
+		q_to_nul >clear.noisybacktrack &&
+	printf "SVNQ%b%b" "\001\001QQQ" "\0200\001\002QQQ" |
+		q_to_nul >clear.noisyadvance &&
+	test_must_fail test-svn-fe -d preimage clear.noisybacktrack 15 &&
+	test-svn-fe -d preimage clear.noisyadvance 15 &&
+	test_cmp empty actual
+'
+
+test_expect_success 'preimage view: reject truncated preimage' '
+	printf "SVNQ%b" "\010QQQQ" | q_to_nul >clear.lateemptyread &&
+	printf "SVNQ%b" "\010\001QQQ" | q_to_nul >clear.latenonemptyread &&
+	printf "SVNQ%b" "\001\010QQQ" | q_to_nul >clear.longread &&
+	test_must_fail test-svn-fe -d preimage clear.lateemptyread 9 &&
+	test_must_fail test-svn-fe -d preimage clear.latenonemptyread 9 &&
+	test_must_fail test-svn-fe -d preimage clear.longread 9
+'
+
 test_done
diff --git a/vcs-svn/svndiff.c b/vcs-svn/svndiff.c
index 249efb6eed..b7c2c8bf53 100644
--- a/vcs-svn/svndiff.c
+++ b/vcs-svn/svndiff.c
@@ -4,6 +4,7 @@
  */
 
 #include "git-compat-util.h"
+#include "sliding_window.h"
 #include "line_buffer.h"
 #include "svndiff.h"
 
@@ -127,6 +128,7 @@ int svndiff0_apply(struct line_buffer *delta, off_t delta_len,
 
 		if (read_offset(delta, &pre_off, &delta_len) ||
 		    read_length(delta, &pre_len, &delta_len) ||
+		    move_window(preimage, pre_off, pre_len) ||
 		    apply_one_window(delta, &delta_len))
 			return -1;
 	}