diff --git a/library/ctr_drbg.c b/library/ctr_drbg.c
index 93a7cdc..23ea07b 100644
--- a/library/ctr_drbg.c
+++ b/library/ctr_drbg.c
@@ -815,7 +815,7 @@
                         return( 1 );                        \
                     }
 
-#define SELF_TEST_OUPUT_DISCARD_LENGTH 64
+#define SELF_TEST_OUTPUT_DISCARD_LENGTH 64
 
 /*
  * Checkup routine
@@ -841,7 +841,7 @@
                                 (void *) entropy_source_pr,
                                 pers_pr, MBEDTLS_CTR_DRBG_KEYSIZE ) );
     mbedtls_ctr_drbg_set_prediction_resistance( &ctx, MBEDTLS_CTR_DRBG_PR_ON );
-    CHK( mbedtls_ctr_drbg_random( &ctx, buf, SELF_TEST_OUPUT_DISCARD_LENGTH ) );
+    CHK( mbedtls_ctr_drbg_random( &ctx, buf, SELF_TEST_OUTPUT_DISCARD_LENGTH ) );
     CHK( mbedtls_ctr_drbg_random( &ctx, buf, sizeof( result_pr ) ) );
     CHK( memcmp( buf, result_pr, sizeof( result_pr ) ) );
 
@@ -866,7 +866,7 @@
                                 (void *) entropy_source_nopr,
                                 pers_nopr, MBEDTLS_CTR_DRBG_KEYSIZE ) );
     CHK( mbedtls_ctr_drbg_reseed( &ctx, NULL, 0 ) );
-    CHK( mbedtls_ctr_drbg_random( &ctx, buf, SELF_TEST_OUPUT_DISCARD_LENGTH ) );
+    CHK( mbedtls_ctr_drbg_random( &ctx, buf, SELF_TEST_OUTPUT_DISCARD_LENGTH ) );
     CHK( mbedtls_ctr_drbg_random( &ctx, buf, sizeof( result_nopr ) ) );
     CHK( memcmp( buf, result_nopr, sizeof( result_nopr ) ) );