diff --git a/src/os/portable/os-impl-bsd-select.c b/src/os/portable/os-impl-bsd-select.c
index dbfb19622..666262155 100644
--- a/src/os/portable/os-impl-bsd-select.c
+++ b/src/os/portable/os-impl-bsd-select.c
@@ -72,16 +72,16 @@
  *
  * returns: Highest numbered file descriptor in the output fd_set
  *-----------------------------------------------------------------*/
-static int OS_FdSet_ConvertIn_Impl(fd_set *os_set, OS_FdSet *OSAL_set)
+static int32 OS_FdSet_ConvertIn_Impl(int *os_maxfd, fd_set *os_set, OS_FdSet *OSAL_set)
 {
     size_t       offset;
     size_t       bit;
     osal_index_t id;
     uint8        objids;
     int          osfd;
-    int          maxfd;
+    int32        status;
 
-    maxfd = -1;
+    status = OS_SUCCESS;
     for (offset = 0; offset < sizeof(OSAL_set->object_ids); ++offset)
     {
         objids = OSAL_set->object_ids[offset];
@@ -94,10 +94,18 @@ static int OS_FdSet_ConvertIn_Impl(fd_set *os_set, OS_FdSet *OSAL_set)
                 osfd = OS_impl_filehandle_table[id].fd;
                 if (osfd >= 0 && OS_impl_filehandle_table[id].selectable)
                 {
-                    FD_SET(osfd, os_set);
-                    if (osfd > maxfd)
+                    if (osfd >= FD_SETSIZE)
+                    {
+                        /* out of range of select() implementation */
+                        status = OS_ERR_OPERATION_NOT_SUPPORTED;
+                    }
+                    else
                     {
-                        maxfd = osfd;
+                        FD_SET(osfd, os_set);
+                        if (osfd > *os_maxfd)
+                        {
+                            *os_maxfd = osfd;
+                        }
                     }
                 }
             }
@@ -106,7 +114,7 @@ static int OS_FdSet_ConvertIn_Impl(fd_set *os_set, OS_FdSet *OSAL_set)
         }
     }
 
-    return maxfd;
+    return status;
 } /* end OS_FdSet_ConvertIn_Impl */
 
 /*----------------------------------------------------------------
@@ -267,6 +275,12 @@ int32 OS_SelectSingle_Impl(const OS_object_token_t *token, uint32 *SelectFlags,
         return OS_ERR_OPERATION_NOT_SUPPORTED;
     }
 
+    if (impl->fd >= FD_SETSIZE)
+    {
+        /* out of range of select() implementation */
+        return OS_ERR_OPERATION_NOT_SUPPORTED;
+    }
+
     if (*SelectFlags != 0)
     {
         FD_ZERO(&wr_set);
@@ -319,34 +333,26 @@ int32 OS_SelectMultiple_Impl(OS_FdSet *ReadSet, OS_FdSet *WriteSet, int32 msecs)
 {
     fd_set wr_set;
     fd_set rd_set;
-    int    osfd;
     int    maxfd;
     int32  return_code;
 
-    /*
-     * This return code will be used if the set(s) do not
-     * contain any file handles capable of select().  It
-     * will be overwritten with the real result of the
-     * select call, if selectable file handles were specified.
-     */
-    return_code = OS_ERR_OPERATION_NOT_SUPPORTED;
     FD_ZERO(&rd_set);
     FD_ZERO(&wr_set);
     maxfd = -1;
     if (ReadSet != NULL)
     {
-        osfd = OS_FdSet_ConvertIn_Impl(&rd_set, ReadSet);
-        if (osfd > maxfd)
+        return_code = OS_FdSet_ConvertIn_Impl(&maxfd, &rd_set, ReadSet);
+        if (return_code != OS_SUCCESS)
         {
-            maxfd = osfd;
+            return return_code;
         }
     }
     if (WriteSet != NULL)
     {
-        osfd = OS_FdSet_ConvertIn_Impl(&wr_set, WriteSet);
-        if (osfd > maxfd)
+        return_code = OS_FdSet_ConvertIn_Impl(&maxfd, &wr_set, WriteSet);
+        if (return_code != OS_SUCCESS)
         {
-            maxfd = osfd;
+            return return_code;
         }
     }
 
@@ -354,6 +360,14 @@ int32 OS_SelectMultiple_Impl(OS_FdSet *ReadSet, OS_FdSet *WriteSet, int32 msecs)
     {
         return_code = OS_DoSelect(maxfd, &rd_set, &wr_set, msecs);
     }
+    else
+    {
+        /*
+         * This return code will be used if the set(s) were
+         * both empty/NULL or otherwise did not contain valid filehandles.
+         */
+        return_code = OS_ERR_INVALID_ID;
+    }
 
     if (return_code == OS_SUCCESS)
     {
diff --git a/src/unit-test-coverage/portable/adaptors/inc/ut-adaptor-portable-posix-io.h b/src/unit-test-coverage/portable/adaptors/inc/ut-adaptor-portable-posix-io.h
index a4cadae82..5acb4ff73 100644
--- a/src/unit-test-coverage/portable/adaptors/inc/ut-adaptor-portable-posix-io.h
+++ b/src/unit-test-coverage/portable/adaptors/inc/ut-adaptor-portable-posix-io.h
@@ -39,5 +39,6 @@
  *
  *****************************************************/
 void UT_PortablePosixIOTest_Set_Selectable(osal_index_t local_id, bool is_selectable);
+void UT_PortablePosixIOTest_Set_FD(osal_index_t local_id, int fd);
 
 #endif /* UT_ADAPTOR_PORTABLE_POSIX_IO_H  */
diff --git a/src/unit-test-coverage/portable/adaptors/src/ut-adaptor-portable-posix-io.c b/src/unit-test-coverage/portable/adaptors/src/ut-adaptor-portable-posix-io.c
index dea9b84d5..feba26469 100644
--- a/src/unit-test-coverage/portable/adaptors/src/ut-adaptor-portable-posix-io.c
+++ b/src/unit-test-coverage/portable/adaptors/src/ut-adaptor-portable-posix-io.c
@@ -35,3 +35,8 @@ void UT_PortablePosixIOTest_Set_Selectable(osal_index_t local_id, bool is_select
 {
     OS_impl_filehandle_table[local_id].selectable = is_selectable;
 }
+
+void UT_PortablePosixIOTest_Set_FD(osal_index_t local_id, int fd)
+{
+    OS_impl_filehandle_table[local_id].fd = fd;
+}
diff --git a/src/unit-test-coverage/portable/src/coveragetest-bsd-select.c b/src/unit-test-coverage/portable/src/coveragetest-bsd-select.c
index fd2f7951c..0367ffb1c 100644
--- a/src/unit-test-coverage/portable/src/coveragetest-bsd-select.c
+++ b/src/unit-test-coverage/portable/src/coveragetest-bsd-select.c
@@ -71,6 +71,13 @@ void Test_OS_SelectSingle_Impl(void)
     UT_SetDataBuffer(UT_KEY(OCS_clock_gettime), &nowtime, sizeof(nowtime), false);
     UT_SetDataBuffer(UT_KEY(OCS_clock_gettime), &latertime, sizeof(latertime), false);
     OSAPI_TEST_FUNCTION_RC(OS_SelectSingle_Impl, (&token, &SelectFlags, 2100), OS_ERROR);
+
+    /* Test cases where the FD exceeds FD_SETSIZE */
+    SelectFlags = OS_STREAM_STATE_READABLE | OS_STREAM_STATE_WRITABLE;
+    UT_PortablePosixIOTest_Set_FD(UT_INDEX_0, OCS_FD_SETSIZE);
+    UT_PortablePosixIOTest_Set_Selectable(UT_INDEX_0, true);
+    OSAPI_TEST_FUNCTION_RC(OS_SelectSingle_Impl, (&token, &SelectFlags, 0), OS_ERR_OPERATION_NOT_SUPPORTED);
+
 } /* end OS_SelectSingle_Impl */
 
 void Test_OS_SelectMultiple_Impl(void)
@@ -81,6 +88,9 @@ void Test_OS_SelectMultiple_Impl(void)
     OS_FdSet ReadSet;
     OS_FdSet WriteSet;
 
+    UT_PortablePosixIOTest_Set_FD(UT_INDEX_0, 0);
+    UT_PortablePosixIOTest_Set_Selectable(UT_INDEX_0, true);
+
     memset(&ReadSet, 0, sizeof(ReadSet));
     memset(&WriteSet, 0xff, sizeof(WriteSet));
     OSAPI_TEST_FUNCTION_RC(OS_SelectMultiple_Impl, (&ReadSet, &WriteSet, 0), OS_SUCCESS);
@@ -88,6 +98,24 @@ void Test_OS_SelectMultiple_Impl(void)
     memset(&WriteSet, 0, sizeof(WriteSet));
     UT_SetDefaultReturnValue(UT_KEY(OCS_select), 0);
     OSAPI_TEST_FUNCTION_RC(OS_SelectMultiple_Impl, (&ReadSet, &WriteSet, 1), OS_ERROR_TIMEOUT);
+
+    /* Test where the FD set is empty */
+    memset(&ReadSet, 0, sizeof(ReadSet));
+    memset(&WriteSet, 0, sizeof(WriteSet));
+    OSAPI_TEST_FUNCTION_RC(OS_SelectMultiple_Impl, (NULL, NULL, 0), OS_ERR_INVALID_ID);
+
+    /* Test cases where the FD exceeds FD_SETSIZE in the read set */
+    UT_PortablePosixIOTest_Set_FD(UT_INDEX_0, OCS_FD_SETSIZE);
+    UT_PortablePosixIOTest_Set_Selectable(UT_INDEX_0, true);
+    memset(&ReadSet, 0xff, sizeof(ReadSet));
+    memset(&WriteSet, 0, sizeof(WriteSet));
+    OSAPI_TEST_FUNCTION_RC(OS_SelectMultiple_Impl, (&ReadSet, &WriteSet, 0), OS_ERR_OPERATION_NOT_SUPPORTED);
+
+    /* Test cases where the FD exceeds FD_SETSIZE in the write set */
+    memset(&ReadSet, 0, sizeof(ReadSet));
+    memset(&WriteSet, 0xff, sizeof(WriteSet));
+    OSAPI_TEST_FUNCTION_RC(OS_SelectMultiple_Impl, (&ReadSet, &WriteSet, 0), OS_ERR_OPERATION_NOT_SUPPORTED);
+
 } /* end OS_SelectMultiple_Impl */
 
 /* ------------------- End of test cases --------------------------------------*/
diff --git a/src/unit-test-coverage/ut-stubs/inc/OCS_sys_select.h b/src/unit-test-coverage/ut-stubs/inc/OCS_sys_select.h
index 531cad372..70d141386 100644
--- a/src/unit-test-coverage/ut-stubs/inc/OCS_sys_select.h
+++ b/src/unit-test-coverage/ut-stubs/inc/OCS_sys_select.h
@@ -35,6 +35,8 @@
 /* constants normally defined in sys/select.h */
 /* ----------------------------------------- */
 
+#define OCS_FD_SETSIZE 10
+
 /* ----------------------------------------- */
 /* types normally defined in sys/select.h */
 /* ----------------------------------------- */
diff --git a/src/unit-test-coverage/ut-stubs/override_inc/sys/select.h b/src/unit-test-coverage/ut-stubs/override_inc/sys/select.h
index 4a2ddb46f..e1e268a88 100644
--- a/src/unit-test-coverage/ut-stubs/override_inc/sys/select.h
+++ b/src/unit-test-coverage/ut-stubs/override_inc/sys/select.h
@@ -50,4 +50,6 @@
 #define FD_CLR   OCS_FD_CLR
 #define FD_ZERO  OCS_FD_ZERO
 
+#define FD_SETSIZE OCS_FD_SETSIZE
+
 #endif /* SELECT_H  */