diff --git a/sched/environ/env_dup.c b/sched/environ/env_dup.c
index 4f773d78e3e..ae58b2a63f8 100644
--- a/sched/environ/env_dup.c
+++ b/sched/environ/env_dup.c
@@ -66,7 +66,6 @@
 int env_dup(FAR struct task_group_s *group, FAR char * const *envcp)
 {
   FAR char **envp = NULL;
-  irqstate_t flags;
   size_t envc = 0;
   size_t size;
   int ret = OK;
@@ -81,7 +80,7 @@ int env_dup(FAR struct task_group_s *group, FAR char * const *envcp)
        * environment may be shared.
        */
 
-      flags = enter_critical_section();
+      nxrmutex_lock(&group->tg_mutex);
 
       /* Count the strings */
 
@@ -142,8 +141,7 @@ int env_dup(FAR struct task_group_s *group, FAR char * const *envcp)
       /* Save the child environment allocation. */
 
       group->tg_envp = envp;
-
-      leave_critical_section(flags);
+      nxrmutex_unlock(&group->tg_mutex);
     }
 
   return ret;
diff --git a/sched/environ/env_getenv.c b/sched/environ/env_getenv.c
index 7cc2805f14e..4513fa347a0 100644
--- a/sched/environ/env_getenv.c
+++ b/sched/environ/env_getenv.c
@@ -63,11 +63,8 @@ FAR char *getenv(FAR const char *name)
   FAR struct tcb_s *rtcb;
   FAR struct task_group_s *group;
   FAR char *pvalue = NULL;
-  irqstate_t flags;
   ssize_t ret = OK;
 
-  flags = enter_critical_section();
-
   /* Verify that a string was passed */
 
   if (name == NULL)
@@ -83,16 +80,26 @@ FAR char *getenv(FAR const char *name)
 
   /* Check if the variable exists */
 
-  if (group == NULL || (ret = env_findvar(group, name)) < 0)
+  if (group == NULL)
     {
       goto errout;
     }
 
+  nxrmutex_lock(&group->tg_mutex);
+  ret = env_findvar(group, name);
+  if (ret < 0)
+    {
+      nxrmutex_unlock(&group->tg_mutex);
+      goto errout;
+    }
+
   /* It does!  Get the value sub-string from the name=value string */
 
   pvalue = strchr(group->tg_envp[ret], '=');
   if (pvalue == NULL)
     {
+      nxrmutex_unlock(&group->tg_mutex);
+
       /* The name=value string has no '='  This is a bug! */
 
       ret = -EINVAL;
@@ -102,11 +109,10 @@ FAR char *getenv(FAR const char *name)
   /* Adjust the pointer so that it points to the value right after the '=' */
 
   pvalue++;
-  leave_critical_section(flags);
+  nxrmutex_unlock(&group->tg_mutex);
   return pvalue;
 
 errout:
-  leave_critical_section(flags);
   set_errno(-ret);
   return NULL;
 }
diff --git a/sched/environ/env_setenv.c b/sched/environ/env_setenv.c
index a64906180ba..ea24bdad99e 100644
--- a/sched/environ/env_setenv.c
+++ b/sched/environ/env_setenv.c
@@ -76,7 +76,6 @@ int setenv(FAR const char *name, FAR const char *value, int overwrite)
   ssize_t envc;
   ssize_t envpc;
   ssize_t ret = OK;
-  irqstate_t flags;
   int varlen;
 
   /* Verify input parameter */
@@ -111,11 +110,12 @@ int setenv(FAR const char *name, FAR const char *value, int overwrite)
 
   /* Get a reference to the thread-private environ in the TCB. */
 
-  flags = enter_critical_section();
   rtcb  = this_task();
   group = rtcb->group;
   DEBUGASSERT(group);
 
+  nxrmutex_lock(&group->tg_mutex);
+
   /* Check if the variable already exists */
 
   if (group->tg_envp && (ret = env_findvar(group, name)) >= 0)
@@ -126,7 +126,7 @@ int setenv(FAR const char *name, FAR const char *value, int overwrite)
         {
           /* No.. then just return success */
 
-          leave_critical_section(flags);
+          nxrmutex_unlock(&group->tg_mutex);
           return OK;
         }
 
@@ -197,13 +197,13 @@ int setenv(FAR const char *name, FAR const char *value, int overwrite)
   /* Now, put the new name=value string into the environment buffer */
 
   snprintf(pvar, varlen, "%s=%s", name, value);
-  leave_critical_section(flags);
+  nxrmutex_unlock(&group->tg_mutex);
   return OK;
 
 errout_with_var:
   group_free(group, pvar);
 errout_with_lock:
-  leave_critical_section(flags);
+  nxrmutex_unlock(&group->tg_mutex);
 errout:
   set_errno(ret);
   return ERROR;
diff --git a/sched/environ/env_unsetenv.c b/sched/environ/env_unsetenv.c
index fb4a206c5a5..5008ef7e01b 100644
--- a/sched/environ/env_unsetenv.c
+++ b/sched/environ/env_unsetenv.c
@@ -63,7 +63,6 @@ int unsetenv(FAR const char *name)
 {
   FAR struct tcb_s *rtcb = this_task();
   FAR struct task_group_s *group = rtcb->group;
-  irqstate_t flags;
   ssize_t idx;
 
   DEBUGASSERT(group);
@@ -78,7 +77,7 @@ int unsetenv(FAR const char *name)
 
   /* Check if the variable exists */
 
-  flags = enter_critical_section();
+  nxrmutex_lock(&group->tg_mutex);
   if (group && (idx = env_findvar(group, name)) >= 0)
     {
       /* It does!  Remove the name=value pair from the environment. */
@@ -86,7 +85,7 @@ int unsetenv(FAR const char *name)
       env_removevar(group, idx);
     }
 
-  leave_critical_section(flags);
+  nxrmutex_unlock(&group->tg_mutex);
   return OK;
 }