diff --git a/asn1/dsp/Makefile.common b/asn1/dsp/Makefile.common
index fed975706f..33538c0e69 100644
--- a/asn1/dsp/Makefile.common
+++ b/asn1/dsp/Makefile.common
@@ -45,7 +45,7 @@ SRC_FILES = \
 
 A2W_FLAGS= -b -e
 
-EXTRA_CNF=
+EXTRA_CNF = \
 	../dap/dap-exp.cnf \
 	../x509if/x509if-exp.cnf \
 	../x509af/x509af-exp.cnf \