diff --git a/src/secp256k1/Makefile.am b/src/secp256k1/Makefile.am
index 7772a4e9d282c..c6150d9de40d9 100644
--- a/src/secp256k1/Makefile.am
+++ b/src/secp256k1/Makefile.am
@@ -75,7 +75,9 @@ TESTS = tests
 endif
 
 if USE_ECMULT_STATIC_PRECOMPUTATION
+CPPFLAGS_FOR_BUILD =
 CPPFLAGS_FOR_BUILD +=-I$(top_srcdir)
+CFLAGS_FOR_BUILD =
 CFLAGS_FOR_BUILD += -Wall -Wextra -Wno-unused-function
 
 gen_context_OBJECTS = gen_context.o