diff --git a/bse/bseengine.cc b/bse/bseengine.cc
index 670abe9c..1acb2ace 100644
--- a/bse/bseengine.cc
+++ b/bse/bseengine.cc
@@ -1286,6 +1286,13 @@ bse_engine_constrain (guint            latency_ms,
    * which are accounted for by block_jitter.
    */
   guint block_size = latency_ms * sample_freq / 1000 / (1 + block_jitter);
+  char *bse_block_size = getenv ("BSE_BLOCK_SIZE");
+  if (bse_block_size)
+    {
+      int bse_block_size_i = atoi (bse_block_size);
+      if (bse_block_size_i)
+        block_size = bse_block_size_i;
+    }
   /* constrain block size */
   block_size = CLAMP (block_size, 8, MIN (BSE_STREAM_MAX_VALUES / 2, sample_freq / (2 * 3)));
   /* adjust block_size */
diff --git a/sfi/platform.cc b/sfi/platform.cc
index 25227133..cba75cd5 100644
--- a/sfi/platform.cc
+++ b/sfi/platform.cc
@@ -752,7 +752,14 @@ this_thread_online_cpus ()
 {
   static int cpus = 0;
   if (!cpus)
-    cpus = sysconf (_SC_NPROCESSORS_ONLN);
+    {
+      char *bse_cpus = getenv ("BSE_CPUS");
+      if (bse_cpus)
+        cpus = atoi (bse_cpus);
+
+      if (!cpus)
+        cpus = sysconf (_SC_NPROCESSORS_ONLN);
+    }
   return cpus;
 }