diff --git a/src/exchange/taler-exchange-aggregator.c b/src/exchange/taler-exchange-aggregator.c
index 0b98a3424..21a29e506 100644
--- a/src/exchange/taler-exchange-aggregator.c
+++ b/src/exchange/taler-exchange-aggregator.c
@@ -1039,10 +1039,10 @@ main (int argc,
                           options,
                           &run, NULL))
   {
-    GNUNET_free ((void *) argv);
+    GNUNET_free_nz ((void *) argv);
     return GR_CMD_LINE_OPTIONS_WRONG;
   }
-  GNUNET_free ((void *) argv);
+  GNUNET_free_nz ((void *) argv);
   return global_ret;
 }
 
diff --git a/src/exchange/taler-exchange-closer.c b/src/exchange/taler-exchange-closer.c
index b4faffb48..542489434 100644
--- a/src/exchange/taler-exchange-closer.c
+++ b/src/exchange/taler-exchange-closer.c
@@ -560,10 +560,10 @@ main (int argc,
                           options,
                           &run, NULL))
   {
-    GNUNET_free ((void *) argv);
+    GNUNET_free_nz ((void *) argv);
     return GR_CMD_LINE_OPTIONS_WRONG;
   }
-  GNUNET_free ((void *) argv);
+  GNUNET_free_nz ((void *) argv);
   return global_ret;
 }
 
diff --git a/src/exchange/taler-exchange-transfer.c b/src/exchange/taler-exchange-transfer.c
index 1793dc988..d21f9ccf1 100644
--- a/src/exchange/taler-exchange-transfer.c
+++ b/src/exchange/taler-exchange-transfer.c
@@ -563,10 +563,10 @@ main (int argc,
                           options,
                           &run, NULL))
   {
-    GNUNET_free ((void *) argv);
+    GNUNET_free_nz ((void *) argv);
     return GR_CMD_LINE_OPTIONS_WRONG;
   }
-  GNUNET_free ((void *) argv);
+  GNUNET_free_nz ((void *) argv);
   return global_ret;
 }
 
diff --git a/src/exchange/taler-exchange-wirewatch.c b/src/exchange/taler-exchange-wirewatch.c
index fba002970..47f2bdb6b 100644
--- a/src/exchange/taler-exchange-wirewatch.c
+++ b/src/exchange/taler-exchange-wirewatch.c
@@ -638,10 +638,10 @@ main (int argc,
                           options,
                           &run, NULL))
   {
-    GNUNET_free ((void *) argv);
+    GNUNET_free_nz ((void *) argv);
     return GR_CMD_LINE_OPTIONS_WRONG;
   }
-  GNUNET_free ((void *) argv);
+  GNUNET_free_nz ((void *) argv);
   return global_ret;
 }
 
diff --git a/src/json/json_wire.c b/src/json/json_wire.c
index f05808194..837263c1e 100644
--- a/src/json/json_wire.c
+++ b/src/json/json_wire.c
@@ -399,7 +399,9 @@ TALER_JSON_merchant_wire_signature_hash (const json_t *wire_s,
                                          struct GNUNET_HashCode *hc)
 {
   const char *payto_uri;
-  const char *salt;
+  const char *salt; /* Current merchant backend will always make the salt
+                       a `struct GNUNET_HashCode`, but *we* do not insist
+                       on that. */
   struct GNUNET_JSON_Specification spec[] = {
     GNUNET_JSON_spec_string ("payto_uri", &payto_uri),
     GNUNET_JSON_spec_string ("salt", &salt),