diff --git a/library/ecdsa.c b/library/ecdsa.c
index 162e62f..5c30380 100644
--- a/library/ecdsa.c
+++ b/library/ecdsa.c
@@ -263,7 +263,7 @@
     mbedtls_mpi *pk = &k, *pr = r;
 
     /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
-    if( !mbedtls_ecdsa_can_do( grp->id ) || grp->N.p == NULL )
+    if( ! mbedtls_ecdsa_can_do( grp->id ) || grp->N.p == NULL )
         return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
 
     /* Make sure d is in range 1..n-1 */
@@ -516,7 +516,7 @@
     mbedtls_mpi_init( &u1 ); mbedtls_mpi_init( &u2 );
 
     /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
-    if( !mbedtls_ecdsa_can_do( grp->id ) || grp->N.p == NULL )
+    if( ! mbedtls_ecdsa_can_do( grp->id ) || grp->N.p == NULL )
         return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
 
     ECDSA_RS_ENTER( ver );