diff --git a/openbsc/src/libmsc/vty_interface_layer3.c b/openbsc/src/libmsc/vty_interface_layer3.c
index 1515aea..71fff93 100644
--- a/openbsc/src/libmsc/vty_interface_layer3.c
+++ b/openbsc/src/libmsc/vty_interface_layer3.c
@@ -547,7 +547,7 @@
 
 	if (strlen(name) > sizeof(subscr->name)-1) {
 		vty_out(vty,
-			"%% NAME is too long, max. %d characters are allowed%s",
+			"%% NAME is too long, max. %zu characters are allowed%s",
 			sizeof(subscr->name)-1, VTY_NEWLINE);
 		return CMD_WARNING;
 	}
@@ -580,7 +580,7 @@
 
 	if (strlen(ext) > sizeof(subscr->extension)-1) {
 		vty_out(vty,
-			"%% EXTENSION is too long, max. %d characters are allowed%s",
+			"%% EXTENSION is too long, max. %zu characters are allowed%s",
 			sizeof(subscr->extension)-1, VTY_NEWLINE);
 		return CMD_WARNING;
 	}
diff --git a/openbsc/src/osmo-bsc_mgcp/mgcp_main.c b/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
index 5f703c2..1c03f27 100644
--- a/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
+++ b/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
@@ -156,7 +156,7 @@
 		return -1;
 	} else if (slen > sizeof(addr)) {
 		fprintf(stderr, "Gateway received message from outerspace: %zu %zu\n",
-			slen, sizeof(addr));
+			(size_t) slen, sizeof(addr));
 		return -1;
 	}
 
diff --git a/openbsc/src/osmo-bsc_nat/bsc_nat_rewrite_trie.c b/openbsc/src/osmo-bsc_nat/bsc_nat_rewrite_trie.c
index faceb59..9291c89 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_nat_rewrite_trie.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat_rewrite_trie.c
@@ -45,10 +45,10 @@
 {
 	struct nat_rewrite_rule *new = &root->rule;
 
-	const size_t len = strlen(rule->prefix);
+	const int len = strlen(rule->prefix);
 	int i;
 
-	if (len == 0) {
+	if (len <= 0) {
 		LOGP(DNAT, LOGL_ERROR, "An empty prefix does not make sense.\n");
 		goto fail;
 	}