diff --git a/NEWS b/NEWS
index 7991c498..885de91c 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,8 @@
 xbps-0.48 (???):
 
+ * libxbps: implemented reverse conflicts. That means that just a single pkg
+   needs to set conflicts to be effective, rather than all involved pkgs.
+
  * libxbps: with -M (--memory-sync opt of xbps-{install,query}) only process
    remote repositories, not local ones.
 
diff --git a/include/xbps_api_impl.h b/include/xbps_api_impl.h
index 077abeff..f7146f23 100644
--- a/include/xbps_api_impl.h
+++ b/include/xbps_api_impl.h
@@ -143,8 +143,7 @@ int HIDDEN xbps_unpack_binary_pkg(struct xbps_handle *, xbps_dictionary_t);
 int HIDDEN xbps_transaction_package_replace(struct xbps_handle *, xbps_array_t);
 int HIDDEN xbps_remove_pkg(struct xbps_handle *, const char *, bool);
 int HIDDEN xbps_register_pkg(struct xbps_handle *, xbps_dictionary_t);
-void HIDDEN xbps_pkg_find_conflicts(struct xbps_handle *, xbps_array_t,
-		xbps_dictionary_t);
+void HIDDEN xbps_transaction_conflicts(struct xbps_handle *, xbps_array_t);
 char HIDDEN *xbps_archive_get_file(struct archive *, struct archive_entry *);
 xbps_dictionary_t HIDDEN xbps_archive_get_dictionary(struct archive *,
 		struct archive_entry *);
diff --git a/lib/Makefile b/lib/Makefile
index 571e621b..bc97817d 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -36,8 +36,9 @@ OBJS += package_unpack.o package_register.o package_script.o verifysig.o
 OBJS += package_msg.o pkgdb_conversion.o transaction_shlibs.o
 OBJS += transaction_commit.o transaction_package_replace.o
 OBJS += transaction_dictionary.o transaction_ops.o transaction_store.o
-OBJS += transaction_revdeps.o pubkey2fp.o package_fulldeptree.o
-OBJS += download.o initend.o pkgdb.o package_conflicts.o
+OBJS += transaction_revdeps.o transaction_conflicts.o
+OBJS += pubkey2fp.o package_fulldeptree.o
+OBJS += download.o initend.o pkgdb.o
 OBJS += plist.o plist_find.o plist_match.o archive.o
 OBJS += plist_remove.o plist_fetch.o util.o util_hash.o 
 OBJS += repo.o repo_pkgdeps.o repo_sync.o
diff --git a/lib/package_conflicts.c b/lib/transaction_conflicts.c
similarity index 63%
rename from lib/package_conflicts.c
rename to lib/transaction_conflicts.c
index c09a6666..192dbb07 100644
--- a/lib/package_conflicts.c
+++ b/lib/transaction_conflicts.c
@@ -1,5 +1,5 @@
 /*-
- * Copyright (c) 2012-2014 Juan Romero Pardines.
+ * Copyright (c) 2012-2015 Juan Romero Pardines.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,10 +31,9 @@
 
 #include "xbps_api_impl.h"
 
-void HIDDEN
-xbps_pkg_find_conflicts(struct xbps_handle *xhp,
-			xbps_array_t unsorted,
-			xbps_dictionary_t pkg_repod)
+static void
+pkg_conflicts_trans(struct xbps_handle *xhp, xbps_array_t array,
+		xbps_dictionary_t pkg_repod)
 {
 	xbps_array_t pkg_cflicts, trans_cflicts;
 	xbps_dictionary_t pkgd, tpkgd;
@@ -76,7 +75,7 @@ xbps_pkg_find_conflicts(struct xbps_handle *xhp,
 			 * the transaction and does not match the pattern,
 			 * ignore it.
 			 */
-			if ((tpkgd = xbps_find_pkg_in_array(unsorted, pkgname, NULL))) {
+			if ((tpkgd = xbps_find_pkg_in_array(array, pkgname, NULL))) {
 				const char *tract, *p;
 
 				xbps_dictionary_get_cstring_nocopy(tpkgd,
@@ -104,8 +103,8 @@ xbps_pkg_find_conflicts(struct xbps_handle *xhp,
 		/*
 		 * Check if current pkg conflicts with any pkg in transaction.
 		 */
-		if ((pkgd = xbps_find_pkg_in_array(unsorted, cfpkg, NULL)) ||
-		    (pkgd = xbps_find_virtualpkg_in_array(xhp, unsorted, cfpkg, NULL))) {
+		if ((pkgd = xbps_find_pkg_in_array(array, cfpkg, NULL)) ||
+		    (pkgd = xbps_find_virtualpkg_in_array(xhp, array, cfpkg, NULL))) {
 			xbps_dictionary_get_cstring_nocopy(pkgd,
 			    "pkgver", &pkgver);
 			pkgname = xbps_pkg_name(pkgver);
@@ -129,3 +128,70 @@ xbps_pkg_find_conflicts(struct xbps_handle *xhp,
 	xbps_object_iterator_release(iter);
 	free(repopkgname);
 }
+
+static int
+pkgdb_conflicts_cb(struct xbps_handle *xhp, xbps_object_t obj,
+		const char *key _unused, void *arg, bool *done _unused)
+{
+	xbps_array_t pkg_cflicts, trans_cflicts, pkgs = arg;
+	xbps_dictionary_t pkgd;
+	xbps_object_t obj2;
+	xbps_object_iterator_t iter;
+	const char *cfpkg, *repopkgver, *pkgver;
+	char *pkgname, *repopkgname, *buf;
+
+	pkg_cflicts = xbps_dictionary_get(obj, "conflicts");
+	if (xbps_array_count(pkg_cflicts) == 0)
+		return 0;
+
+	trans_cflicts = xbps_dictionary_get(xhp->transd, "conflicts");
+	xbps_dictionary_get_cstring_nocopy(obj, "pkgver", &repopkgver);
+	repopkgname = xbps_pkg_name(repopkgver);
+	assert(repopkgname);
+
+	iter = xbps_array_iterator(pkg_cflicts);
+	assert(iter);
+
+	while ((obj2 = xbps_object_iterator_next(iter))) {
+		cfpkg = xbps_string_cstring_nocopy(obj2);
+		if ((pkgd = xbps_find_pkg_in_array(pkgs, cfpkg, NULL)) ||
+		    (pkgd = xbps_find_virtualpkg_in_array(xhp, pkgs, cfpkg, NULL))) {
+			xbps_dictionary_get_cstring_nocopy(pkgd,
+			    "pkgver", &pkgver);
+			pkgname = xbps_pkg_name(pkgver);
+			assert(pkgname);
+			if (strcmp(pkgname, repopkgname) == 0) {
+				free(pkgname);
+				continue;
+			}
+			free(pkgname);
+			xbps_dbg_printf(xhp, "found conflicting pkgs in "
+			    "transaction %s <-> %s\n", pkgver, repopkgver);
+			buf = xbps_xasprintf("CONFLICT: %s with "
+			   "%s in transaction", repopkgver, pkgver);
+			if (!xbps_match_string_in_array(trans_cflicts, buf))
+				xbps_array_add_cstring(trans_cflicts, buf);
+
+			free(buf);
+			continue;
+		}
+	}
+	xbps_object_iterator_release(iter);
+	free(repopkgname);
+	return 0;
+}
+
+void HIDDEN
+xbps_transaction_conflicts(struct xbps_handle *xhp, xbps_array_t pkgs)
+{
+	xbps_dictionary_t pkgd;
+	unsigned int i;
+
+	/* find conflicts in transaction */
+	for (i = 0; i < xbps_array_count(pkgs); i++) {
+		pkgd = xbps_array_get(pkgs, i);
+		pkg_conflicts_trans(xhp, pkgs, pkgd);
+	}
+	/* find conflicts in pkgdb */
+	(void)xbps_pkgdb_foreach_cb_multi(xhp, pkgdb_conflicts_cb, pkgs);
+}
diff --git a/lib/transaction_dictionary.c b/lib/transaction_dictionary.c
index 222d49eb..d92e935d 100644
--- a/lib/transaction_dictionary.c
+++ b/lib/transaction_dictionary.c
@@ -319,11 +319,10 @@ xbps_transaction_prepare(struct xbps_handle *xhp)
 			return ENODEV;
 		}
 	}
-	for (i = 0; i < xbps_array_count(pkgs); i++)
-		xbps_pkg_find_conflicts(xhp, pkgs, xbps_array_get(pkgs, i));
 	/*
 	 * If there are package conflicts bail out.
 	 */
+	xbps_transaction_conflicts(xhp, pkgs);
 	array = xbps_dictionary_get(xhp->transd, "conflicts");
 	if (xbps_array_count(array))
 		return EAGAIN;
diff --git a/tests/xbps/libxbps/shell/Kyuafile b/tests/xbps/libxbps/shell/Kyuafile
index d9ea33c0..53a4bf14 100644
--- a/tests/xbps/libxbps/shell/Kyuafile
+++ b/tests/xbps/libxbps/shell/Kyuafile
@@ -21,3 +21,4 @@ atf_test_program{name="update_shlibs"}
 atf_test_program{name="update_hold"}
 atf_test_program{name="update_repolock"}
 atf_test_program{name="cyclic_deps"}
+atf_test_program{name="conflicts"}
diff --git a/tests/xbps/libxbps/shell/Makefile b/tests/xbps/libxbps/shell/Makefile
index d88daf52..4e14e2b5 100644
--- a/tests/xbps/libxbps/shell/Makefile
+++ b/tests/xbps/libxbps/shell/Makefile
@@ -6,7 +6,7 @@ TESTSHELL = conf_files_test issue6_test issue18_test issue20_test remove_test
 TESTSHELL+= replace_test installmode_test obsoletefiles_test
 TESTSHELL+= issue31_test scripts_test incorrect_deps_test
 TESTSHELL+= vpkg_test install_test preserve_files_test configure_test
-TESTSHELL+= update_shlibs update_hold update_repolock cyclic_deps
+TESTSHELL+= update_shlibs update_hold update_repolock cyclic_deps conflicts
 EXTRA_FILES = Kyuafile
 
 include $(TOPDIR)/mk/test.mk
diff --git a/tests/xbps/libxbps/shell/conflicts.sh b/tests/xbps/libxbps/shell/conflicts.sh
new file mode 100644
index 00000000..cf62f828
--- /dev/null
+++ b/tests/xbps/libxbps/shell/conflicts.sh
@@ -0,0 +1,88 @@
+#!/usr/bin/env atf-sh
+
+atf_test_case conflicts_trans
+
+conflicts_trans_head() {
+	atf_set "descr" "Tests for pkg conflicts: conflicting pkgs in transaction"
+}
+
+conflicts_trans_body() {
+	mkdir some_repo
+	mkdir -p pkg_{A,B}/usr/bin
+	cd some_repo
+	xbps-create -A noarch -n A-1.0_1 -s "A pkg" --conflicts "B>=0" ../pkg_A
+	atf_check_equal $? 0
+	xbps-create -A noarch -n B-1.0_1 -s "B pkg" ../pkg_B
+	atf_check_equal $? 0
+
+	xbps-rindex -d -a $PWD/*.xbps
+	atf_check_equal $? 0
+	cd ..
+
+	xbps-install -r root --repository=$PWD/some_repo -dy A B
+	# EAGAIN, conflicts.
+	atf_check_equal $? 11
+	# 0 pkgs installed.
+	xbps-query -r root -l|wc -l
+	atf_check_equal $(xbps-query -r root -l|wc -l) 0
+}
+
+atf_test_case conflicts_installed
+
+conflicts_installed_head() {
+	atf_set "descr" "Tests for pkg conflicts: installed pkg conflicts with pkg in transaction"
+}
+
+conflicts_installed_body() {
+	mkdir some_repo
+	mkdir -p pkg_{A,B}/usr/bin
+	cd some_repo
+	xbps-create -A noarch -n A-1.0_1 -s "A pkg" --conflicts "B>=0" ../pkg_A
+	atf_check_equal $? 0
+	xbps-create -A noarch -n B-1.0_1 -s "B pkg" ../pkg_B
+	atf_check_equal $? 0
+
+	xbps-rindex -d -a $PWD/*.xbps
+	atf_check_equal $? 0
+	cd ..
+
+	xbps-install -r root --repository=$PWD/some_repo -dy A
+	atf_check_equal $? 0
+	xbps-install -r root --repository=$PWD/some_repo -dy B
+	atf_check_equal $? 11
+	xbps-query -r root -l|wc -l
+	atf_check_equal $(xbps-query -r root -l|wc -l) 1
+}
+
+atf_test_case conflicts_trans_installed
+
+conflicts_trans_installed_head() {
+	atf_set "descr" "Tests for pkg conflicts: pkg in transaction conflicts with installed pkg"
+}
+
+conflicts_trans_installed_body() {
+	mkdir some_repo
+	mkdir -p pkg_{A,B}/usr/bin
+	cd some_repo
+	xbps-create -A noarch -n A-1.0_1 -s "A pkg" --conflicts "B>=0" ../pkg_A
+	atf_check_equal $? 0
+	xbps-create -A noarch -n B-1.0_1 -s "B pkg" ../pkg_B
+	atf_check_equal $? 0
+
+	xbps-rindex -d -a $PWD/*.xbps
+	atf_check_equal $? 0
+	cd ..
+
+	xbps-install -r root --repository=$PWD/some_repo -dy B
+	atf_check_equal $? 0
+	xbps-install -r root --repository=$PWD/some_repo -dy A
+	atf_check_equal $? 11
+	xbps-query -r root -l|wc -l
+	atf_check_equal $(xbps-query -r root -l|wc -l) 1
+}
+
+atf_init_test_cases() {
+	atf_add_test_case conflicts_trans
+	atf_add_test_case conflicts_trans_installed
+	atf_add_test_case conflicts_installed
+}