diff --git a/tests/test-c-plugin/test-c-plugin.c b/tests/test-c-plugin/test-c-plugin.c
index 62c5f50..05d95d0 100644
--- a/tests/test-c-plugin/test-c-plugin.c
+++ b/tests/test-c-plugin/test-c-plugin.c
@@ -692,7 +692,7 @@ prof_on_message_stanza_send(const char *const stanza)
     create_win();
 
     char *str = "fired -> prof_on_message_stanza_send: ";
-    char buf[strlen(str) + strlen(stanza)];
+    char buf[strlen(str) + strlen(stanza) + 1];
     sprintf(buf, "%s%s", str, stanza);
     prof_win_show(plugin_win, buf);
 
@@ -707,7 +707,7 @@ prof_on_message_stanza_receive(const char *const stanza)
     create_win();
 
     char *str = "fired -> prof_on_message_stanza_receive: ";
-    char buf[strlen(str) + strlen(stanza)];
+    char buf[strlen(str) + strlen(stanza) + 1];
     sprintf(buf, "%s%s", str, stanza);
     prof_win_show(plugin_win, buf);
 
@@ -720,7 +720,7 @@ prof_on_presence_stanza_send(const char *const stanza)
     create_win();
 
     char *str = "fired -> prof_on_presence_stanza_send: ";
-    char buf[strlen(str) + strlen(stanza)];
+    char buf[strlen(str) + strlen(stanza) + 1];
     sprintf(buf, "%s%s", str, stanza);
     prof_win_show(plugin_win, buf);
 
@@ -733,7 +733,7 @@ prof_on_presence_stanza_receive(const char *const stanza)
     create_win();
 
     char *str = "fired -> prof_on_presence_stanza_receive: ";
-    char buf[strlen(str) + strlen(stanza)];
+    char buf[strlen(str) + strlen(stanza) + 1];
     sprintf(buf, "%s%s", str, stanza);
     prof_win_show(plugin_win, buf);
 
@@ -746,7 +746,7 @@ prof_on_iq_stanza_send(const char *const stanza)
     create_win();
 
     char *str = "fired -> prof_on_iq_stanza_send: ";
-    char buf[strlen(str) + strlen(stanza)];
+    char buf[strlen(str) + strlen(stanza) + 1];
     sprintf(buf, "%s%s", str, stanza);
     prof_win_show(plugin_win, buf);
 
@@ -759,7 +759,7 @@ prof_on_iq_stanza_receive(const char *const stanza)
     create_win();
 
     char *str = "fired -> prof_on_iq_stanza_receive: ";
-    char buf[strlen(str) + strlen(stanza)];
+    char buf[strlen(str) + strlen(stanza) + 1];
     sprintf(buf, "%s%s", str, stanza);
     prof_win_show(plugin_win, buf);