diff --git a/libc-test/semver/espidf.txt b/libc-test/semver/espidf.txt
index 74f0d0cb5266d..cdef4f09bc0eb 100644
--- a/libc-test/semver/espidf.txt
+++ b/libc-test/semver/espidf.txt
@@ -31,6 +31,7 @@ SIGQUIT
 SIGSEGV
 SIGTERM
 SOL_SOCKET
+SOMAXCONN
 cmsghdr
 dirent
 eventfd
diff --git a/src/unix/newlib/espidf/mod.rs b/src/unix/newlib/espidf/mod.rs
index 9bec89a7d78d4..d3b01b883566b 100644
--- a/src/unix/newlib/espidf/mod.rs
+++ b/src/unix/newlib/espidf/mod.rs
@@ -97,6 +97,8 @@ pub const SIGHUP: c_int = 1;
 pub const SIGQUIT: c_int = 3;
 pub const NSIG: size_t = 32;
 
+pub const SOMAXCONN: c_int = 128;
+
 extern "C" {
     pub fn pthread_create(
         native: *mut crate::pthread_t,