diff --git a/library/error.c b/library/error.c
index 564490e..097260c 100644
--- a/library/error.c
+++ b/library/error.c
@@ -856,7 +856,7 @@
     if( use_ret == -(MBEDTLS_ERR_SHA1_HW_ACCEL_FAILED) )
         mbedtls_snprintf( buf, buflen, "SHA1 - SHA-1 hardware accelerator failed" );
     if( use_ret == -(MBEDTLS_ERR_SHA1_BAD_INPUT_DATA) )
-        mbedtls_snprintf( buf, buflen, "SHA1 - Invalid input data" );
+        mbedtls_snprintf( buf, buflen, "SHA1 - SHA-1 input data was malformed" );
 #endif /* MBEDTLS_SHA1_C */
 
 #if defined(MBEDTLS_SHA256_C)