diff --git a/qpkg/TODO b/qpkg/TODO
index e88fadc..f95cc41 100644
--- a/qpkg/TODO
+++ b/qpkg/TODO
@@ -3,6 +3,9 @@ Still left to do
 
 - check whether introducing a new package would cause a conflict
 
+  Update: conflicts among the packages considered for installation are now
+  checked.
+
 - compile the list of conflicts of installed packages
 
 - handle Provides:
diff --git a/qpkg/prereq.c b/qpkg/prereq.c
index 56b8ac9..d7e330a 100644
--- a/qpkg/prereq.c
+++ b/qpkg/prereq.c
@@ -93,6 +93,7 @@ static int satisfies(const struct pkg *pkg, const struct ref *ref)
 		return 0;
 	if (!ref->version)
 		return 1;
+	/* @@@ error in the database, not qpkg's fault */
 	assert(pkg->version);
 	cmp = comp_versions(pkg->version, ref->version);
 //fprintf(stderr, "%.*s <%d> %.*s\n",
@@ -112,7 +113,14 @@ static int satisfies(const struct pkg *pkg, const struct ref *ref)
 
 static int conflicts(const struct pkg *pkg, const struct list *conf)
 {
-	/* @@@ */
+	const struct ref *ref;
+
+	while (conf) {
+		for (ref = conf->refs; ref; ref = ref->next)
+			if (satisfies(pkg, ref))
+				return 1;
+		conf = conf->next;
+	}
 	return 0;
 }
 
@@ -219,9 +227,14 @@ struct pkg **prereq(struct pkg *pkg)
 		.pkg = pkg,
 		.next = NULL
 	};
+	struct list conf = {
+		.refs = pkg->conflicts,
+		.next = NULL
+	};
+
 	/* @@@ make list of pre-existing conflicts */
 	pkg->flags |= QPKG_ADDING;
-	resolve(NULL, pkg->depends, &stack, NULL);
+	resolve(NULL, pkg->depends, &stack, &conf);
 	pkg->flags &= ~QPKG_ADDING;
 	free(installs);
 	return best;
diff --git a/qpkg/test/conflict b/qpkg/test/conflict
new file mode 100755
index 0000000..aa72f81
--- /dev/null
+++ b/qpkg/test/conflict
@@ -0,0 +1,157 @@
+#!/bin/sh
+. ./Common
+
+###############################################################################
+
+qpkg_fail "direct conflict precludes resolution" prereq A <<EOF
+Package: B
+Version: 0
+Architecture: test
+Filename: B
+
+Package: A
+Version: 0
+Architecture: test
+Depends: B
+Conflicts: B
+Filename: A
+EOF
+expect <<EOF
+can't resolve A
+EOF
+
+###############################################################################
+
+qpkg_fail "indirect conflict precludes resolution" prereq A <<EOF
+Package: C
+Version: 0
+Architecture: test
+Filename: C
+
+Package: B
+Version: 0
+Architecture: test
+Depends: C
+Filename: B
+
+Package: A
+Version: 0
+Architecture: test
+Depends: B
+Conflicts: C
+Filename: A
+EOF
+expect <<EOF
+can't resolve A
+EOF
+
+###############################################################################
+
+qpkg_fail "aggregation of conflicts" prereq A <<EOF
+Package: C
+Version: 0
+Architecture: test
+Filename: C
+
+Package: B
+Version: 0
+Architecture: test
+Depends: C
+Conflicts: C
+Filename: B
+
+Package: A
+Version: 0
+Architecture: test
+Depends: B
+Filename: A
+EOF
+expect <<EOF
+can't resolve A
+EOF
+
+###############################################################################
+
+qpkg_fail "conflicts honor version (match)" prereq A <<EOF
+Package: B
+Version: 1
+Architecture: test
+Filename: B
+
+Package: A
+Version: 0
+Architecture: test
+Depends: B
+Conflicts: B (= 1)
+Filename: A
+EOF
+expect <<EOF
+can't resolve A
+EOF
+
+###############################################################################
+
+qpkg "conflicts honor version (mismatch)" prereq A <<EOF
+Package: B
+Version: 1
+Architecture: test
+Filename: B
+
+Package: A
+Version: 0
+Architecture: test
+Depends: B
+Conflicts: B (= 0)
+Filename: A
+EOF
+expect <<EOF
+B
+EOF
+
+###############################################################################
+
+qpkg "conflict trumps preference (1)" prereq foo <<EOF
+Package: bar
+Version: 0
+Architecture: test
+Filename: bar_0
+
+Package: bar
+Version: 1
+Architecture: test
+Filename: bar_1
+
+Package: foo
+Version: 0
+Architecture: test
+Depends: bar
+Conflicts: bar (>= 1)
+Filename: foo
+EOF
+expect <<EOF
+bar_0
+EOF
+
+###############################################################################
+
+qpkg "conflict trumps preference (2)" prereq foo <<EOF
+Package: bar
+Version: 1
+Architecture: test
+Filename: bar_1
+
+Package: bar
+Version: 0
+Architecture: test
+Filename: bar_0
+
+Package: foo
+Version: 0
+Architecture: test
+Depends: bar
+Conflicts: bar (>= 1)
+Filename: foo
+EOF
+expect <<EOF
+bar_0
+EOF