diff --git a/Module.cc b/Module.cc
index f828b9e148..ffe2c2e119 100644
--- a/Module.cc
+++ b/Module.cc
@@ -92,7 +92,7 @@ const svector<PEIdent*>& Module::get_port(unsigned idx) const
 
 unsigned Module::find_port(const char*name) const
 {
-      assert(name != "");
+      assert(name != 0);
       for (unsigned idx = 0 ;  idx < ports.count() ;  idx += 1) {
 	    if (ports[idx] == 0) {
 		    /* It is possible to have undeclared ports. These
diff --git a/vvp/sfunc.cc b/vvp/sfunc.cc
index 3c20775ae3..7ce4c87c29 100644
--- a/vvp/sfunc.cc
+++ b/vvp/sfunc.cc
@@ -95,7 +95,7 @@ static int make_vpi_argv(unsigned argc, vpiHandle*vpi_argv,
 	    break;
 
 	  default:
-	    fprintf(stderr, "Unsupported type %c(%d).\n", *cp);
+	    fprintf(stderr, "Unsupported type %c(%d).\n", *cp, *cp);
 	    assert(0);
 	    break;
       }
@@ -118,7 +118,7 @@ static int make_vpi_argv(unsigned argc, vpiHandle*vpi_argv,
 		}
 
 		default:
-		  fprintf(stderr, "Unsupported type %c(%d).\n", *cp);
+		  fprintf(stderr, "Unsupported type %c(%d).\n", *cp, *cp);
 		  assert(0);
 	    }
 	    idx += 1;
diff --git a/vvp/udp.cc b/vvp/udp.cc
index 93aecae855..4920631fa2 100644
--- a/vvp/udp.cc
+++ b/vvp/udp.cc
@@ -228,7 +228,7 @@ void vvp_udp_comb_s::compile_table(char**tab)
 	    cur.maskx = 0;
 	    if (port_count() > 8*sizeof(cur.mask0)) {
 		  fprintf(stderr, "internal error: primitive port count=%u "
-			  " > %d\n", port_count(), sizeof(cur.mask0));
+			  " > %zu\n", port_count(), sizeof(cur.mask0));
 		  assert(port_count() <= 8*sizeof(cur.mask0));
 	    }
 	    for (unsigned pp = 0 ;  pp < port_count() ;  pp += 1) {
diff --git a/vvp/vvp_net.cc b/vvp/vvp_net.cc
index 2b0b726e7d..c96d1d6a4b 100644
--- a/vvp/vvp_net.cc
+++ b/vvp/vvp_net.cc
@@ -1455,7 +1455,7 @@ void vvp_fun_signal_base::recv_long(vvp_net_ptr_t ptr, long bit)
 		  release(ptr, false);
 		  break;
 		default:
-		  fprintf(stderr, "Unsupported command %d.\n", bit);
+		  fprintf(stderr, "Unsupported command %ld.\n", bit);
 		  assert(0);
 		  break;
 	    }