diff --git a/src/unix/thread.c b/src/unix/thread.c
index 3def2945..ada2ffc8 100644
--- a/src/unix/thread.c
+++ b/src/unix/thread.c
@@ -37,6 +37,10 @@
 #include <sys/sem.h>
 #endif
 
+#ifdef __GLIBC__
+#include <gnu/libc-version.h>  /* gnu_get_libc_version() */
+#endif
+
 #undef NANOSEC
 #define NANOSEC ((uint64_t) 1e9)
 
@@ -502,26 +506,138 @@ int uv_sem_trywait(uv_sem_t* sem) {
 
 #else /* !(defined(__APPLE__) && defined(__MACH__)) */
 
-int uv_sem_init(uv_sem_t* sem, unsigned int value) {
+#ifdef __GLIBC__
+
+/* Hack around https://sourceware.org/bugzilla/show_bug.cgi?id=12674
+ * by providing a custom implementation for glibc < 2.21 in terms of other
+ * concurrency primitives.
+ * Refs: https://github.com/nodejs/node/issues/19903 */
+
+/* To preserve ABI compatibility, we treat the uv_sem_t as storage for
+ * a pointer to the actual struct we're using underneath. */
+
+static uv_once_t glibc_version_check_once = UV_ONCE_INIT;
+static int glibc_needs_custom_semaphore = 0;
+
+static void glibc_version_check(void) {
+  const char* version = gnu_get_libc_version();
+  glibc_needs_custom_semaphore =
+      version[0] == '2' && version[1] == '.' &&
+      atoi(version + 2) < 21;
+}
+
+#else /* !defined(__GLIBC__) */
+
+#define glibc_needs_custom_semaphore 0
+
+#endif
+
+typedef struct uv_semaphore_s {
+  uv_mutex_t mutex;
+  uv_cond_t cond;
+  unsigned int value;
+} uv_semaphore_t;
+
+
+STATIC_ASSERT(sizeof(uv_sem_t) >= sizeof(uv_semaphore_t*));
+
+static int uv__custom_sem_init(uv_sem_t* sem_, unsigned int value) {
+  int err;
+  uv_semaphore_t* sem;
+
+  sem = uv__malloc(sizeof(*sem));
+  if (sem == NULL)
+    return UV_ENOMEM;
+
+  if ((err = uv_mutex_init(&sem->mutex)) != 0) {
+    uv__free(sem);
+    return err;
+  }
+
+  if ((err = uv_cond_init(&sem->cond)) != 0) {
+    uv_mutex_destroy(&sem->mutex);
+    uv__free(sem);
+    return err;
+  }
+
+  sem->value = value;
+  *(uv_semaphore_t**)sem_ = sem;
+  return 0;
+}
+
+
+static void uv__custom_sem_destroy(uv_sem_t* sem_) {
+  uv_semaphore_t* sem;
+
+  sem = *(uv_semaphore_t**)sem_;
+  uv_cond_destroy(&sem->cond);
+  uv_mutex_destroy(&sem->mutex);
+  uv__free(sem);
+}
+
+
+static void uv__custom_sem_post(uv_sem_t* sem_) {
+  uv_semaphore_t* sem;
+
+  sem = *(uv_semaphore_t**)sem_;
+  uv_mutex_lock(&sem->mutex);
+  sem->value++;
+  if (sem->value == 1)
+    uv_cond_signal(&sem->cond);
+  uv_mutex_unlock(&sem->mutex);
+}
+
+
+static void uv__custom_sem_wait(uv_sem_t* sem_) {
+  uv_semaphore_t* sem;
+
+  sem = *(uv_semaphore_t**)sem_;
+  uv_mutex_lock(&sem->mutex);
+  while (sem->value == 0)
+    uv_cond_wait(&sem->cond, &sem->mutex);
+  sem->value--;
+  uv_mutex_unlock(&sem->mutex);
+}
+
+
+static int uv__custom_sem_trywait(uv_sem_t* sem_) {
+  uv_semaphore_t* sem;
+
+  sem = *(uv_semaphore_t**)sem_;
+  if (uv_mutex_trylock(&sem->mutex) != 0)
+    return UV_EAGAIN;
+
+  if (sem->value == 0) {
+    uv_mutex_unlock(&sem->mutex);
+    return UV_EAGAIN;
+  }
+
+  sem->value--;
+  uv_mutex_unlock(&sem->mutex);
+
+  return 0;
+}
+
+static int uv__sem_init(uv_sem_t* sem, unsigned int value) {
   if (sem_init(sem, 0, value))
     return UV__ERR(errno);
   return 0;
 }
 
 
-void uv_sem_destroy(uv_sem_t* sem) {
+static void uv__sem_destroy(uv_sem_t* sem) {
   if (sem_destroy(sem))
     abort();
 }
 
 
-void uv_sem_post(uv_sem_t* sem) {
+static void uv__sem_post(uv_sem_t* sem) {
   if (sem_post(sem))
     abort();
 }
 
 
-void uv_sem_wait(uv_sem_t* sem) {
+static void uv__sem_wait(uv_sem_t* sem) {
   int r;
 
   do
@@ -533,7 +649,7 @@ void uv_sem_wait(uv_sem_t* sem) {
 }
 
 
-int uv_sem_trywait(uv_sem_t* sem) {
+static int uv__sem_trywait(uv_sem_t* sem) {
   int r;
 
   do
@@ -549,6 +665,49 @@ int uv_sem_trywait(uv_sem_t* sem) {
   return 0;
 }
 
+int uv_sem_init(uv_sem_t* sem, unsigned int value) {
+#ifdef __GLIBC__
+  uv_once(&glibc_version_check_once, glibc_version_check);
+#endif
+
+  if (glibc_needs_custom_semaphore)
+    return uv__custom_sem_init(sem, value);
+  else
+    return uv__sem_init(sem, value);
+}
+
+
+void uv_sem_destroy(uv_sem_t* sem) {
+  if (glibc_needs_custom_semaphore)
+    uv__custom_sem_destroy(sem);
+  else
+    uv__sem_destroy(sem);
+}
+
+
+void uv_sem_post(uv_sem_t* sem) {
+  if (glibc_needs_custom_semaphore)
+    uv__custom_sem_post(sem);
+  else
+    uv__sem_post(sem);
+}
+
+
+void uv_sem_wait(uv_sem_t* sem) {
+  if (glibc_needs_custom_semaphore)
+    uv__custom_sem_wait(sem);
+  else
+    uv__sem_wait(sem);
+}
+
+
+int uv_sem_trywait(uv_sem_t* sem) {
+  if (glibc_needs_custom_semaphore)
+    return uv__custom_sem_trywait(sem);
+  else
+    return uv__sem_trywait(sem);
+}
+
 #endif /* defined(__APPLE__) && defined(__MACH__) */