diff --git a/Makefile b/Makefile
index 733e33a..3655131 100644
--- a/Makefile
+++ b/Makefile
@@ -33,7 +33,7 @@ else ifeq ($(ARCH), arm)
 	$(CARM) $(COMMON) $(LIBCROSS) -D $(CURVE) $(MULTI_SET)
 
 else ifeq ($(shell uname), Darwin)
-	$(CC) $(COMMON) $(LIBMAC)-D $(CURVE) $(MULTI_SET)
+	$(CC) $(COMMON) $(LIBMAC) -D $(CURVE) $(MULTI_SET) -D IS_MAC_OS
 
 else
 	$(CC) $(COMMON) $(LIB) -D $(CURVE) $(MULTI_SET)
diff --git a/src/gro16/prover.c b/src/gro16/prover.c
index c77e31a..edde8a8 100644
--- a/src/gro16/prover.c
+++ b/src/gro16/prover.c
@@ -111,7 +111,11 @@ void mul_exp(struct mulExpResult *result, mpz_t *uwProof, proving_key pk)
         if(i >= (nPublic + nConst)) mpz_to_fr(&uwFactorPublic[i-(nPublic + nConst)], &uw[i]);
     }
 
-    int num_threads = get_nprocs();
+    #ifdef IS_MAC_OS
+        int num_threads = 8;
+    #else
+        int num_threads = get_nprocs();
+    #endif
 
     mclBnG1_mulVecMT(&result->uwA1, pk.A1, uwFactor, M, num_threads);
     mclBnG1_mulVecMT(&result->uwB1, pk.B1, uwFactor, M, num_threads);