diff --git a/src/debug.c b/src/debug.c
index d7604a7c..37baabb0 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -379,6 +379,9 @@ _gpgme_debug_buffer (int lvl, const char *const fmt,
   if (!_gpgme_debug_trace ())
     return;
 
+  if (!buffer)
+    return;
+
   while (idx < len)
     {
       char str[51];
diff --git a/src/genkey.c b/src/genkey.c
index ffca7e8e..0108aab0 100644
--- a/src/genkey.c
+++ b/src/genkey.c
@@ -283,9 +283,9 @@ gpgme_op_genkey_start (gpgme_ctx_t ctx, const char *parms,
 
   TRACE_BEG2 (DEBUG_CTX, "gpgme_op_genkey_start", ctx,
 	      "pubkey=%p, seckey=%p", pubkey, seckey);
-  TRACE_LOGBUF (parms, strlen (parms));
+  TRACE_LOGBUF (parms, parms? strlen (parms):0);
 
-  if (!ctx)
+  if (!ctx || parms)
     return TRACE_ERR (gpg_error (GPG_ERR_INV_ARG));
 
   err = genkey_start (ctx, 0, parms, pubkey, seckey);
@@ -304,7 +304,7 @@ gpgme_op_genkey (gpgme_ctx_t ctx, const char *parms, gpgme_data_t pubkey,
 
   TRACE_BEG2 (DEBUG_CTX, "gpgme_op_genkey", ctx,
 	      "pubkey=%p, seckey=%p", pubkey, seckey);
-  TRACE_LOGBUF (parms, strlen (parms));
+  TRACE_LOGBUF (parms, parms? strlen (parms):0);
 
   if (!ctx)
     return TRACE_ERR (gpg_error (GPG_ERR_INV_ARG));