Index: src/libspf2/spf_compile.c
--- src/libspf2/spf_compile.c.orig
+++ src/libspf2/spf_compile.c
@@ -582,7 +582,7 @@ SPF_c_parse_macro(SPF_server_t *spf_server,
 		switch (src[idx]) {
 		case '%':
 			if (spf_server->debug > 3)
-				SPF_debugf("Adding literal %%");
+				SPF_debugf("%s", "Adding literal %");
 			SPF_ENSURE_STRING_AVAIL(1);
 			*dst++ = '%';
 			ds_len++;
@@ -591,7 +591,7 @@ SPF_c_parse_macro(SPF_server_t *spf_server,
 			
 		case '_':
 			if (spf_server->debug > 3)
-				SPF_debugf("Adding literal space");
+				SPF_debugf("%s", "Adding literal space");
 			SPF_ENSURE_STRING_AVAIL(1);
 			*dst++ = ' ';
 			ds_len++;
@@ -600,7 +600,7 @@ SPF_c_parse_macro(SPF_server_t *spf_server,
 
 		case '-':
 			if (spf_server->debug > 3)
-				SPF_debugf("Adding escaped space");
+				SPF_debugf("%s", "Adding escaped space");
 			SPF_ENSURE_STRING_AVAIL(3);
 			*dst++ = '%'; *dst++ = '2'; *dst++ = '0';
 			ds_len += 3;
