--- a/doc/specs/Makefile.am
+++ b/doc/specs/Makefile.am
@@ -12,9 +12,9 @@
 AM_YFLAGS = -d
 
 CC = @CC_FOR_BUILD@
-CPPFLAGS = @BUILD_CPPFLAGS@
-CFLAGS = @BUILD_CFLAGS@
-LDFLAGS = @BUILD_LDFLAGS@
+AM_CPPFLAGS = @BUILD_CPPFLAGS@
+AM_CFLAGS = @BUILD_CFLAGS@
+AM_LDFLAGS = @BUILD_LDFLAGS@
 
 BUILT_SOURCES = parse_y.h