diff --git a/include/picolibc-freertos.h b/include/picolibc-freertos.h
index 472d71e9932..467f7a97091 100644
--- a/include/picolibc-freertos.h
+++ b/include/picolibc-freertos.h
@@ -43,22 +43,43 @@
 
 #define configTLS_BLOCK_TYPE               void *
 
+#define picolibcTLS_SIZE                   ( ( portPOINTER_SIZE_TYPE ) _tls_size() )
+#define picolibcSTACK_ALIGNMENT_MASK       ( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK )
+
+#if __PICOLIBC_MAJOR__ > 1 || __PICOLIBC_MINOR__ >= 8
+
+/* Picolibc 1.8 and newer have explicit alignment values provided
+ * by the _tls_align() inline */
+    #define picolibcTLS_ALIGNMENT_MASK    ( ( portPOINTER_SIZE_TYPE ) ( _tls_align() - 1 ) )
+#else
+
+/* For older Picolibc versions, use the general port alignment value */
+    #define picolibcTLS_ALIGNMENT_MASK    ( ( portPOINTER_SIZE_TYPE ) portBYTE_ALIGNMENT_MASK )
+#endif
+
 /* Allocate thread local storage block off the end of the
 * stack. The _tls_size() function returns the size (in
 * bytes) of the total TLS area used by the application */
 #if ( portSTACK_GROWTH < 0 )
-    #define configINIT_TLS_BLOCK( xTLSBlock, pxTopOfStack )                                            \
-    do {                                                                                               \
-        pxTopOfStack = ( StackType_t * ) ( ( ( portPOINTER_SIZE_TYPE ) pxTopOfStack ) - _tls_size() ); \
-        xTLSBlock = pxTopOfStack;                                                                      \
-        _init_tls( xTLSBlock );                                                                        \
+
+    #define configINIT_TLS_BLOCK( xTLSBlock, pxTopOfStack )                             \
+    do {                                                                                \
+        pxTopOfStack = ( StackType_t * ) ( ( ( ( portPOINTER_SIZE_TYPE ) pxTopOfStack ) \
+                                             - picolibcTLS_SIZE ) & ~                   \
+                                           configMAX( picolibcSTACK_ALIGNMENT_MASK,     \
+                                                      picolibcTLS_ALIGNMENT_MASK ) );   \
+        xTLSBlock = pxTopOfStack;                                                       \
+        _init_tls( xTLSBlock );                                                         \
     } while( 0 )
 #else /* portSTACK_GROWTH */
-    #define configINIT_TLS_BLOCK( xTLSBlock, pxTopOfStack )                                            \
-    do {                                                                                               \
-        xTLSBlock = pxTopOfStack;                                                                      \
-        pxTopOfStack = ( StackType_t * ) ( ( ( portPOINTER_SIZE_TYPE ) pxTopOfStack ) + _tls_size() ); \
-        _init_tls( xTLSBlock );                                                                        \
+    #define configINIT_TLS_BLOCK( xTLSBlock, pxTopOfStack )                                          \
+    do {                                                                                             \
+        xTLSBlock = ( void * ) ( ( ( portPOINTER_SIZE_TYPE ) pxTopOfStack +                          \
+                                   picolibcTLS_ALIGNMENT_MASK ) & ~picolibcTLS_ALIGNMENT_MASK );     \
+        pxTopOfStack = ( StackType_t * ) ( ( ( ( ( portPOINTER_SIZE_TYPE ) xTLSBlock ) +             \
+                                               picolibcTLS_SIZE ) + picolibcSTACK_ALIGNMENT_MASK ) & \
+                                           ~picolibcSTACK_ALIGNMENT_MASK );                          \
+        _init_tls( xTLSBlock );                                                                      \
     } while( 0 )
 #endif /* portSTACK_GROWTH */