diff --git a/lib/pace/Makefile b/lib/pace/Makefile
index 5a1588ef93..a7ac753d28 100644
--- a/lib/pace/Makefile
+++ b/lib/pace/Makefile
@@ -21,7 +21,7 @@ OBJ =   $(SRC:.cpp=.o)
 
 
 # ------ SETTINGS ------
-CXXFLAGS = -O3 -fPIC -Isrc/ML-PACE -I$(YAML_CPP_INC) -I$(WIGNER_CPP_INC) -I$(CNPY_CPP_INC) -DEXTRA_C_PROJECTIONS
+CXXFLAGS = -O3 -fPIC -Isrc/ML-PACE -I$(YAML_CPP_INC) -I$(WIGNER_CPP_INC) -I$(CNPY_CPP_INC) -DEXTRA_C_PROJECTIONS -DCOMPUTE_B_GRAD
 
 ARCHIVE =	ar
 ARCHFLAG =	-rc