diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9f19bf90..7a730557 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -258,6 +258,7 @@ if(MI_DEBUG_UBSAN)
   if(CMAKE_BUILD_TYPE MATCHES "Debug")
     if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
       message(STATUS "Build with undefined-behavior sanitizer (MI_DEBUG_UBSAN=ON)")
+      list(APPEND mi_defines MI_UBSAN=1)
       list(APPEND mi_cflags -fsanitize=undefined -g -fno-sanitize-recover=undefined)
       list(APPEND mi_libraries -fsanitize=undefined)
       if (NOT MI_USE_CXX)
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 0247c76f..01ad7a1b 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -112,7 +112,7 @@ jobs:
         CC: clang
         CXX: clang++
         BuildType: debug-tsan-clang-cxx
-        cmakeExtraArgs: -DCMAKE_BUILD_TYPE=Debug -DMI_USE_CXX=ON -DMI_DEBUG_TSAN=ON
+        cmakeExtraArgs: -DCMAKE_BUILD_TYPE=RelWithDebInfo -DMI_USE_CXX=ON -DMI_DEBUG_TSAN=ON
       
   steps:
   - task: CMake@1
diff --git a/src/alloc.c b/src/alloc.c
index d2f4a927..afd9e923 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -584,6 +584,7 @@ mi_decl_nodiscard void* mi_new_reallocn(void* p, size_t newcount, size_t size) {
 #ifdef __cplusplus
 void* _mi_externs[] = {
   (void*)&_mi_page_malloc,
+  (void*)&_mi_page_malloc_zero,
   (void*)&_mi_heap_malloc_zero,
   (void*)&_mi_heap_malloc_zero_ex,
   (void*)&mi_malloc,
diff --git a/src/arena-abandoned.c b/src/arena-abandon.c
similarity index 99%
rename from src/arena-abandoned.c
rename to src/arena-abandon.c
index 465a074d..eaa8c7c9 100644
--- a/src/arena-abandoned.c
+++ b/src/arena-abandon.c
@@ -13,8 +13,6 @@ terms of the MIT license. A copy of the license can be found in the file
 #include "bitmap.h"
 #endif
 
-typedef struct mi_arena_s mi_arena_t;
-
 // Minimal exports for arena-abandoned.
 size_t      mi_arena_id_index(mi_arena_id_t id);
 mi_arena_t* mi_arena_from_index(size_t idx);
diff --git a/src/arena.c b/src/arena.c
index 9111243e..d2039623 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -62,7 +62,7 @@ static mi_decl_cache_align _Atomic(mi_arena_t*) mi_arenas[MI_MAX_ARENAS];
 static mi_decl_cache_align _Atomic(size_t)      mi_arena_count; // = 0
 
 #define MI_IN_ARENA_C
-#include "arena-abandoned.c"
+#include "arena-abandon.c"
 #undef MI_IN_ARENA_C
 
 /* -----------------------------------------------------------
diff --git a/test/test-stress.c b/test/test-stress.c
index c6a64130..1e144bd0 100644
--- a/test/test-stress.c
+++ b/test/test-stress.c
@@ -25,14 +25,21 @@ terms of the MIT license.
 // > mimalloc-test-stress [THREADS] [SCALE] [ITER]
 //
 // argument defaults
-#if !defined(MI_TSAN)
+#if defined(MI_TSAN)          // with thread-sanitizer reduce the threads to test within the azure pipeline limits
+static int THREADS = 8;       
+static int SCALE   = 25;
+static int ITER    = 200;
+#elif defined(MI_UBSAN)       // with undefined behavious sanitizer reduce parameters to stay within the azure pipeline limits
+static int THREADS = 8;       
+static int SCALE   = 25;
+static int ITER    = 20;
+#else
 static int THREADS = 32;      // more repeatable if THREADS <= #processors
-#else                         // with thread-sanitizer reduce the defaults for azure pipeline limits
-static int THREADS = 8;
-#endif
-
 static int SCALE   = 25;      // scaling factor
 static int ITER    = 50;      // N full iterations destructing and re-creating all threads
+#endif
+
+
 
 #define STRESS                // undefine for leak test