diff --git a/README.md b/README.md
index 7e61d6419..5a1fc5fca 100755
--- a/README.md
+++ b/README.md
@@ -202,6 +202,7 @@ For previous versions, please read:
 
 ## V3 changes
 
+* v3.0, 2020-10-31, Fix [#509][bug #509], Always malloc stack on heap. 3.0.153
 * v3.0, 2020-10-31, Remove some global elements for debugging. 3.0.152
 * v3.0, 2020-10-31, Use global _srs_server for debugging. 3.0.151
 * v3.0, 2020-10-31, Refine source cid, track previous one. 3.0.150
diff --git a/trunk/.gitignore b/trunk/.gitignore
index c5ff54605..a67b91615 100644
--- a/trunk/.gitignore
+++ b/trunk/.gitignore
@@ -44,4 +44,4 @@ srs
 /configure.sh
 /janus
 *.dump
-
+bug
diff --git a/trunk/auto/depends.sh b/trunk/auto/depends.sh
index 8e6ba482d..6429ee455 100755
--- a/trunk/auto/depends.sh
+++ b/trunk/auto/depends.sh
@@ -347,6 +347,8 @@ else
     echo "Build ST without UDP sendmmsg support."
     _ST_EXTRA_CFLAGS="$_ST_EXTRA_CFLAGS -UMD_HAVE_SENDMMSG -U_GNU_SOURCE"
 fi
+# Always alloc on heap, @see https://github.com/ossrs/srs/issues/509#issuecomment-719931676
+_ST_EXTRA_CFLAGS="$_ST_EXTRA_CFLAGS -DMALLOC_STACK"
 # Pass the global extra flags.
 if [[ $SRS_EXTRA_FLAGS != '' ]]; then
     _ST_EXTRA_CFLAGS="$_ST_EXTRA_CFLAGS $SRS_EXTRA_FLAGS"
diff --git a/trunk/src/app/srs_app_server.cpp b/trunk/src/app/srs_app_server.cpp
index 767b78cf9..3aeef041b 100644
--- a/trunk/src/app/srs_app_server.cpp
+++ b/trunk/src/app/srs_app_server.cpp
@@ -803,18 +803,6 @@ srs_error_t SrsServer::initialize_st()
 {
     srs_error_t err = srs_success;
 
-    // @remark, st alloc segment use mmap, which only support 32757 threads,
-    // if need to support more, for instance, 100k threads, define the macro MALLOC_STACK.
-    // TODO: FIXME: maybe can use "sysctl vm.max_map_count" to refine.
-#define __MMAP_MAX_CONNECTIONS 32756
-    if (_srs_config->get_max_connections() > __MMAP_MAX_CONNECTIONS) {
-        srs_error("st mmap for stack allocation must <= %d threads, "
-                  "@see Makefile of st for MALLOC_STACK, please build st manually by "
-                  "\"make EXTRA_CFLAGS=-DMALLOC_STACK linux-debug\"", __MMAP_MAX_CONNECTIONS);
-        return srs_error_new(ERROR_ST_EXCEED_THREADS, "%d exceed max %d threads",
-            _srs_config->get_max_connections(), __MMAP_MAX_CONNECTIONS);
-    }
-    
     // check asprocess.
     bool asprocess = _srs_config->get_asprocess();
     if (asprocess && ppid == 1) {
diff --git a/trunk/src/core/srs_core_version3.hpp b/trunk/src/core/srs_core_version3.hpp
index 4f7a26305..37451726f 100644
--- a/trunk/src/core/srs_core_version3.hpp
+++ b/trunk/src/core/srs_core_version3.hpp
@@ -24,6 +24,6 @@
 #ifndef SRS_CORE_VERSION3_HPP
 #define SRS_CORE_VERSION3_HPP
 
-#define SRS_VERSION3_REVISION 152
+#define SRS_VERSION3_REVISION 153
 
 #endif