diff --git a/include/mbedtls/platform_util.h b/include/mbedtls/platform_util.h
index 6f09209..8d00eba 100644
--- a/include/mbedtls/platform_util.h
+++ b/include/mbedtls/platform_util.h
@@ -262,6 +262,10 @@
  *
  *              Duration of the delay is random as number of variable increments
  *              is randomized.
+ *
+ * \note        This function works only if the MBEDTLS_FI_COUNTERMEASURES flag
+ *              is defined in the configuration. Otherwise, the function does
+ *              nothing.
  */
 void mbedtls_platform_random_delay( void );
 
diff --git a/library/platform_util.c b/library/platform_util.c
index 641172a..3fa9437 100644
--- a/library/platform_util.c
+++ b/library/platform_util.c
@@ -255,6 +255,7 @@
 
 void mbedtls_platform_random_delay( void )
 {
+#if defined(MBEDTLS_FI_COUNTERMEASURES)
     uint32_t rn_1, rn_2, rn_3;
     volatile size_t i = 0;
     uint8_t shift;
@@ -276,6 +277,9 @@
             rn_3 = ( rn_3 << shift ) | ( rn_3 >> ( 32 - shift ) );
         rn_2 ^= rn_3;
     } while( i < rn_1 || rn_2 == 0 || rn_3 == 0 );
+
+#endif /* MBEDTLS_FI_COUNTERMEASURES */
+    return;
 }
 
 #if defined(MBEDTLS_HAVE_TIME_DATE) && !defined(MBEDTLS_PLATFORM_GMTIME_R_ALT)