diff --git a/driver-vpi/main.c b/driver-vpi/main.c
index bfd1ec77b..1785fbf78 100644
--- a/driver-vpi/main.c
+++ b/driver-vpi/main.c
@@ -236,7 +236,9 @@ static int GetRegistryKey(char *key, char **value)
 	}
 	regKeyBuffer[regKeySize] = 0;		/* makes sure there is a trailing NULL */
 
-	lrv = RegQueryValueEx(hkKey,key,NULL,&regKeyType,regKeyBuffer,&regKeySize);
+	/* This needs an unsigned char *, but for MinGW the char is signed. */
+	lrv = RegQueryValueEx(hkKey, key, NULL, &regKeyType,
+	                      (unsigned char *) regKeyBuffer, &regKeySize);
 	if ((lrv != ERROR_SUCCESS) || (regKeyType != REG_SZ) || (!regKeySize)) {
 		lrv = RegCloseKey(hkKey);
 		free(regKeyBuffer);
@@ -269,7 +271,9 @@ static void SetRegistryKey(char *key, char *value)
 		&res) != ERROR_SUCCESS)
 			return;
 
-	RegSetValueEx(hkKey,key,0,REG_SZ,value,strlen(value)+1);
+	/* This needs an unsigned char *, but for MinGW the char is signed. */
+	RegSetValueEx(hkKey, key, 0, REG_SZ, (unsigned char *) value,
+	              strlen(value)+1);
 	RegCloseKey(hkKey);
 
 	printf("info:  storing %s in Windows' registry entry\n",value);
diff --git a/tgt-vvp/draw_vpi.c b/tgt-vvp/draw_vpi.c
index 1266b43b8..94d8e851f 100644
--- a/tgt-vvp/draw_vpi.c
+++ b/tgt-vvp/draw_vpi.c
@@ -161,7 +161,11 @@ static int get_vpi_taskfunc_signal_arg(struct args_info *result,
 			      fprintf(stderr, "%s:%u: tgt-vvp warning: V0.9 "
 			                      "may give incorrect results for "
 			                      "an array select with a signed "
+#ifdef __MINGW32__  /* MinGW does not know about z. */
+			                      "index less than %u bits.\n",
+#else
 			                      "index less than %zu bits.\n",
+#endif
 			                      ivl_expr_file(expr),
 			                      ivl_expr_lineno(expr),
 			                      8*sizeof(int));
@@ -230,7 +234,11 @@ static int get_vpi_taskfunc_signal_arg(struct args_info *result,
 		      (ivl_expr_width(bexpr) < 8*sizeof(int))) {
 			fprintf(stderr, "%s:%u: tgt-vvp warning: V0.9 may give "
 			                "incorrect results for a select with a "
+#ifdef __MINGW32__  /* MinGW does not know about z. */
+			                "signed index less than %u bits.\n",
+#else
 			                "signed index less than %zu bits.\n",
+#endif
 			                ivl_expr_file(expr),
 			                ivl_expr_lineno(expr),
 			                8*sizeof(int));
diff --git a/tgt-vvp/vvp_scope.c b/tgt-vvp/vvp_scope.c
index fbdc4778f..d34eb6eee 100644
--- a/tgt-vvp/vvp_scope.c
+++ b/tgt-vvp/vvp_scope.c
@@ -1692,7 +1692,11 @@ static void draw_lpm_part(ivl_lpm_t net)
 	    if (ivl_lpm_signed(net) && width_of_nexus(sel) < 8*sizeof(int)) {
 		  fprintf(stderr, "%s:%u: tgt-vvp warning: V0.9 may give "
 		                  "incorrect results for a select with a "
+#ifdef __MINGW32__  /* MinGW does not know about z. */
+		                  "signed index less than %u bits.\n",
+#else
 		                  "signed index less than %zu bits.\n",
+#endif
 		                  ivl_lpm_file(net), ivl_lpm_lineno(net),
 		                  8*sizeof(int));
 	    }
diff --git a/vvp/main.cc b/vvp/main.cc
index 6f0649d23..a452fcd33 100644
--- a/vvp/main.cc
+++ b/vvp/main.cc
@@ -366,16 +366,28 @@ int main(int argc, char*argv[])
       }
 
       if (verbose_flag) {
+#ifdef __MINGW32__  /* MinGW does not know about z. */
+	    vpi_mcd_printf(1, " ... %8lu functors (net_fun pool=%u bytes)\n",
+#else
 	    vpi_mcd_printf(1, " ... %8lu functors (net_fun pool=%zu bytes)\n",
+#endif
 			   count_functors, size_vvp_net_funs);
 	    vpi_mcd_printf(1, "           %8lu logic\n",  count_functors_logic);
 	    vpi_mcd_printf(1, "           %8lu bufif\n",  count_functors_bufif);
 	    vpi_mcd_printf(1, "           %8lu resolv\n",count_functors_resolv);
 	    vpi_mcd_printf(1, "           %8lu signals\n", count_functors_sig);
+#ifdef __MINGW32__  /* MinGW does not know about z. */
+	    vpi_mcd_printf(1, " ... %8lu opcodes (%u bytes)\n",
+#else
 	    vpi_mcd_printf(1, " ... %8lu opcodes (%zu bytes)\n",
+#endif
 	                   count_opcodes, size_opcodes);
 	    vpi_mcd_printf(1, " ... %8lu nets\n",     count_vpi_nets);
+#ifdef __MINGW32__  /* MinGW does not know about z. */
+	    vpi_mcd_printf(1, " ... %8lu vvp_nets (%u bytes)\n",
+#else
 	    vpi_mcd_printf(1, " ... %8lu vvp_nets (%zu bytes)\n",
+#endif
 			   count_vvp_nets, size_vvp_nets);
 	    vpi_mcd_printf(1, " ... %8lu arrays (%lu words)\n",
 			   count_net_arrays, count_net_array_words);