diff --git a/src/backend/utils/adt/pg_locale_builtin.c b/src/backend/utils/adt/pg_locale_builtin.c
index f51768830cd..df5612b5a2d 100644
--- a/src/backend/utils/adt/pg_locale_builtin.c
+++ b/src/backend/utils/adt/pg_locale_builtin.c
@@ -91,7 +91,7 @@ strtitle_builtin(char *dest, size_t destsize, const char *src, ssize_t srclen,
 {
 	struct WordBoundaryState wbstate = {
 		.str = src,
-		.len = srclen,
+		.len = (srclen < 0) ? strlen(src) : srclen,
 		.offset = 0,
 		.posix = !locale->info.builtin.casemap_full,
 		.init = false,
diff --git a/src/common/unicode/case_test.c b/src/common/unicode/case_test.c
index fdfb62e8552..6dfc4d130ea 100644
--- a/src/common/unicode/case_test.c
+++ b/src/common/unicode/case_test.c
@@ -303,7 +303,7 @@ tfunc_title(char *dst, size_t dstsize, const char *src,
 {
 	struct WordBoundaryState wbstate = {
 		.str = src,
-		.len = srclen,
+		.len = (srclen < 0) ? strlen(src) : srclen,
 		.offset = 0,
 		.init = false,
 		.prev_alnum = false,