diff --git a/init/init.c++ b/init/init.c++
index d30f5f3f..6f15398f 100644
--- a/init/init.c++
+++ b/init/init.c++
@@ -62,9 +62,10 @@ char* read_single_line(FILE* fp)
 	return ret;
 }
 
+__attribute__((format(printf, 1, 2)))
 char* print_string(const char* format, ...)
 {
-	char* ret = NULL;
+	char* ret;
 	va_list ap;
 	va_start(ap, format);
 	int status = vasprintf(&ret, format, ap);
diff --git a/tix/util.h b/tix/util.h
index e9f0551f..b3f1fb70 100644
--- a/tix/util.h
+++ b/tix/util.h
@@ -369,6 +369,7 @@ bool dictionary_append_file_path(string_array_t* sa, const char* path)
 	return true;
 }
 
+__attribute__((format(printf, 1, 2)))
 char* print_string(const char* format, ...)
 {
 	va_list ap;
diff --git a/trianglix/trianglix.cpp b/trianglix/trianglix.cpp
index 9a3a16e6..349de8a3 100644
--- a/trianglix/trianglix.cpp
+++ b/trianglix/trianglix.cpp
@@ -60,12 +60,14 @@ bool use_runes = false;
 bool configured_use_runes = false;
 uint8_t font[FONT_CHARSIZE * FONT_NUMCHARS];
 
+__attribute__((format(printf, 1, 2)))
 char* print_string(const char* format, ...)
 {
-	char* ret = NULL;
+	char* ret;
 	va_list ap;
 	va_start(ap, format);
-	vasprintf(&ret, format, ap);
+	if ( vasprintf(&ret, format, ap) < 0 )
+		ret = NULL;
 	va_end(ap);
 	return ret;
 }