diff --git a/libobs/obs-cocoa.m b/libobs/obs-cocoa.m
index 4019aed089394a..0bc4ffe1ebb3e4 100644
--- a/libobs/obs-cocoa.m
+++ b/libobs/obs-cocoa.m
@@ -166,7 +166,9 @@ void log_system_info(void)
 static bool dstr_from_cfstring(struct dstr *str, CFStringRef ref)
 {
     CFIndex length = CFStringGetLength(ref);
-    CFIndex max_size = CFStringGetMaximumSizeForEncoding(length, kCFStringEncodingUTF8);
+    CFIndex max_size = CFStringGetMaximumSizeForEncoding(length, kCFStringEncodingUTF8) + 1;
+    assert(max_size > 0);
+
     dstr_reserve(str, max_size);
 
     if (!CFStringGetCString(ref, str->array, max_size, kCFStringEncodingUTF8))