diff --git a/sal/esp32/soc_shell_base.c b/sal/esp32/soc_shell_base.c
index 634357c..12b0165 100644
--- a/sal/esp32/soc_shell_base.c
+++ b/sal/esp32/soc_shell_base.c
@@ -20,10 +20,21 @@
 #include "task.h"
 
 /* Unsigned integers.  */
+#ifndef PRIu8
 #define PRIu8 "u"
+#endif
+
+#ifndef PRIu16
 #define PRIu16 "u"
+#endif
+
+#ifndef PRIu32
 #define PRIu32 "u"
+#endif
+
+#ifndef PRIu64
 #define PRIu64 __PRI64_PREFIX "u"
+#endif
 
 SH_CMD_FN(_base_free);
 SH_CMD_FN(_base_heap);