diff --git a/call_traits_test.cpp b/call_traits_test.cpp
index dca67bb..b99838c 100644
--- a/call_traits_test.cpp
+++ b/call_traits_test.cpp
@@ -410,6 +410,8 @@ unsigned int expected_failures = 6;
 unsigned int expected_failures = 2;
 #elif defined(__GNUC__)
 unsigned int expected_failures = 4;
+#elif defined(__HP_aCC)
+unsigned int expected_failures = 20;
 #else
 unsigned int expected_failures = 0;
 #endif