diff --git a/source/dub/package_.d b/source/dub/package_.d
index 439b25a..b00e4a7 100644
--- a/source/dub/package_.d
+++ b/source/dub/package_.d
@@ -211,6 +211,20 @@
 		return ret.data;
 	}
 
+	const(Dependency[string]) getDependencies(string config)
+	const {
+		Dependency[string] ret;
+		foreach (k, v; m_info.buildSettings.dependencies)
+			ret[k] = v;
+		foreach (ref conf; m_info.configurations)
+			if (conf.name == config) {
+				foreach (k, v; conf.buildSettings.dependencies)
+					ret[k] = v;
+				break;
+			}
+		return ret;
+	}
+
 	/** Overwrites the packge description file using the default filename with the current information.
 	*/
 	void storeInfo()
diff --git a/source/dub/project.d b/source/dub/project.d
index d156c53..d701bd0 100644
--- a/source/dub/project.d
+++ b/source/dub/project.d
@@ -402,8 +402,15 @@
 		}
 
 		// check for conflicts (packages missing in the final configuration graph)
-		foreach (p; getTopologicalPackageList())
-			enforce(p.name in ret, "Could not resolve configuration for package "~p.name);
+		void checkPacksRec(in Package pack) {
+			auto pc = pack.name in ret;
+			enforce(pc !is null, "Could not resolve configuration for package "~pack.name);
+			foreach (p, dep; pack.getDependencies(*pc)) {
+				auto deppack = getDependency(p, dep.optional);
+				if (deppack) checkPacksRec(deppack);
+			}
+		}
+		checkPacksRec(m_rootPackage);
 
 		return ret;
 	}