diff --git a/include/haproxy/defaults.h b/include/haproxy/defaults.h
index 6dc5167d8..a8e5e5780 100644
--- a/include/haproxy/defaults.h
+++ b/include/haproxy/defaults.h
@@ -34,10 +34,6 @@
 #define MAX_THREADS_PER_GROUP 1
 
 #else
-/* threads enabled, max_threads defaults to long bits */
-#ifndef MAX_THREADS
-#define MAX_THREADS LONGBITS
-#endif
 
 /* theoretical limit is 64, though we'd rather not push it too far for now
  * as some structures might be enlarged to be indexed per group. Let's start
@@ -48,9 +44,18 @@
 #ifndef MAX_TGROUPS
 #define MAX_TGROUPS 16
 #endif
+
 #define MAX_THREADS_PER_GROUP LONGBITS
+
+/* threads enabled, max_threads defaults to long bits for 1 tgroup or 4 times
+ * long bits if more tgroups are enabled.
+ */
+#ifndef MAX_THREADS
+#define MAX_THREADS ((((MAX_TGROUPS) > 1) ? 4 : 1) * (MAX_THREADS_PER_GROUP))
 #endif
 
+#endif // USE_THREAD
+
 /*
  * BUFSIZE defines the size of a read and write buffer. It is the maximum
  * amount of bytes which can be stored by the proxy for each stream. However,