diff --git a/include/polarssl/ctr_drbg.h b/include/polarssl/ctr_drbg.h
index b47d389..4c0fc17 100644
--- a/include/polarssl/ctr_drbg.h
+++ b/include/polarssl/ctr_drbg.h
@@ -43,7 +43,11 @@
                                             /**< The seed length (counter + AES key)            */
 
 #if !defined(POLARSSL_CONFIG_OPTIONS)
-#define CTR_DRBG_ENTROPY_LEN        48      /**< Amount of entropy used per seed by default */
+#if defined(POLARSSL_SHA512_C)
+#define CTR_DRBG_ENTROPY_LEN        48      /**< Amount of entropy used per seed by default (48 with SHA-512, 32 with SHA-256) */
+#else
+#define CTR_DRBG_ENTROPY_LEN        32      /**< Amount of entropy used per seed by default (48 with SHA-512, 32 with SHA-256) */
+#endif
 #define CTR_DRBG_RESEED_INTERVAL    10000   /**< Interval before reseed is performed by default */
 #define CTR_DRBG_MAX_INPUT          256     /**< Maximum number of additional input bytes */
 #define CTR_DRBG_MAX_REQUEST        1024    /**< Maximum number of requested bytes per call */