diff --git a/bernoulli.h b/bernoulli.h
index 04809083..3c2a6886 100644
--- a/bernoulli.h
+++ b/bernoulli.h
@@ -34,9 +34,9 @@
 #include "arith.h"
 #include "fmprb.h"
 
-extern long bernoulli_cache_num;
+extern long __thread bernoulli_cache_num;
 
-extern fmpq * bernoulli_cache;
+extern __thread fmpq * bernoulli_cache;
 
 void bernoulli_cache_compute(long n);
 
diff --git a/bernoulli/cache_compute.c b/bernoulli/cache_compute.c
index b064beac..7df3c1d0 100644
--- a/bernoulli/cache_compute.c
+++ b/bernoulli/cache_compute.c
@@ -25,9 +25,9 @@
 
 #include "bernoulli.h"
 
-long bernoulli_cache_num = 0;
+__thread long bernoulli_cache_num = 0;
 
-fmpq * bernoulli_cache = NULL;
+__thread fmpq * bernoulli_cache = NULL;
 
 void
 bernoulli_cache_compute(long n)