diff --git a/library/pem.c b/library/pem.c
index b2c16c2..76905b3 100644
--- a/library/pem.c
+++ b/library/pem.c
@@ -389,6 +389,8 @@
 
 void pem_free( pem_context *ctx )
 {
+    if ( ctx->buf != NULL )
+        polarssl_zeroize( ctx->buf, ctx->buflen );
     polarssl_free( ctx->buf );
     polarssl_free( ctx->info );