diff --git a/arch/sandbox/cpu/os.c b/arch/sandbox/cpu/os.c
index 725b505177d33938cee5cf4ce8308bb13bf11c9a..2e2fc58a1ba86630307dec70613e47571820a57b 100644
--- a/arch/sandbox/cpu/os.c
+++ b/arch/sandbox/cpu/os.c
@@ -143,7 +143,7 @@ void *os_malloc(size_t length)
 	return hdr + 1;
 }
 
-void *os_free(void *ptr)
+void os_free(void *ptr)
 {
 	struct os_mem_hdr *hdr = ptr;
 
diff --git a/include/os.h b/include/os.h
index b65fba430144d2587c068756fd8bfbd001799354..d6d6e5794e479460f9881f59e90fc453bb519e8e 100644
--- a/include/os.h
+++ b/include/os.h
@@ -113,7 +113,7 @@ void *os_malloc(size_t length);
  *
  * \param ptr		Pointer to memory block to free
  */
-void *os_free(void *ptr);
+void os_free(void *ptr);
 
 /**
  * Reallocate previously-allocated memory to increase/decrease space