diff --git a/test/regress/test_perl_ex.cpp b/test/regress/test_perl_ex.cpp
index 3bf104b7..6aa31684 100644
--- a/test/regress/test_perl_ex.cpp
+++ b/test/regress/test_perl_ex.cpp
@@ -131,7 +131,7 @@ void test_conditionals()
    TEST_INVALID_REGEX("(?<!*|^)", perl);
    TEST_INVALID_REGEX("(?<!*|A)", perl);
    TEST_INVALID_REGEX("(?<=?|A)", perl);
-   TEST_INVALID_REGEX("(?<=*|\B)", perl);
+   TEST_INVALID_REGEX("(?<=*|\\B)", perl);
 }
 
 void test_options()