diff --git a/main.c b/main.c
index ae5da56..dcde276 100644
--- a/main.c
+++ b/main.c
@@ -213,28 +213,48 @@ print_digraph_node(pkg_t *pkg, void *unused, unsigned int flags)
 	}
 }
 
-static void
+static bool
 apply_digraph(pkg_t *world, void *unused, int maxdepth, unsigned int flags)
 {
+	int eflag;
+
 	printf("graph deptree {\n");
 	printf("edge [color=blue len=7.5 fontname=Sans fontsize=8]\n");
 	printf("node [fontname=Sans fontsize=8]\n");
 
-	pkg_traverse(world, print_digraph_node, unused, maxdepth, flags);
+	eflag = pkg_traverse(world, print_digraph_node, unused, maxdepth, flags);
+
+	if (eflag != PKG_ERRF_OK)
+		return false;
 
 	printf("}\n");
+	return true;
 }
 
-static void
+static bool
 apply_modversion(pkg_t *world, void *unused, int maxdepth, unsigned int flags)
 {
-	pkg_traverse(world, print_modversion, unused, maxdepth, flags);
+	int eflag;
+
+	eflag = pkg_traverse(world, print_modversion, unused, maxdepth, flags);
+
+	if (eflag != PKG_ERRF_OK)
+		return false;
+
+	return true;
 }
 
-static void
+static bool
 apply_variables(pkg_t *world, void *unused, int maxdepth, unsigned int flags)
 {
-	pkg_traverse(world, print_variables, unused, maxdepth, flags);
+	int eflag;
+
+	eflag = pkg_traverse(world, print_variables, unused, maxdepth, flags);
+
+	if (eflag != PKG_ERRF_OK)
+		return false;
+
+	return true;
 }
 
 typedef struct {
@@ -263,44 +283,57 @@ print_variable(pkg_t *pkg, void *data, unsigned int flags)
 	}
 }
 
-static void
+static bool
 apply_variable(pkg_t *world, void *variable, int maxdepth, unsigned int flags)
 {
+	int eflag;
+
 	var_request_t req = {
 		.variable = variable,
 	};
 
 	*req.buf = '\0';
 
-	pkg_traverse(world, print_variable, &req, maxdepth, flags);
+	eflag = pkg_traverse(world, print_variable, &req, maxdepth, flags);
+	if (eflag != PKG_ERRF_OK)
+		return false;
+
 	printf("%s\n", req.buf);
+	return true;
 }
 
-static void
+static bool
 apply_cflags(pkg_t *world, void *list_head, int maxdepth, unsigned int flags)
 {
 	pkg_fragment_t **head = list_head;
 	pkg_fragment_t *list;
 
 	list = pkg_cflags(world, head, maxdepth, flags | PKGF_SEARCH_PRIVATE);
+	if (list == NULL)
+		return false;
+
 	print_cflags(list);
 
 	pkg_fragment_free(list);
+	return true;
 }
 
-static void
+static bool
 apply_libs(pkg_t *world, void *list_head, int maxdepth, unsigned int flags)
 {
 	pkg_fragment_t **head = list_head;
 	pkg_fragment_t *list;
 
 	list = pkg_libs(world, head, maxdepth, flags);
+	if (list == NULL)
+		return false;
 	print_libs(list);
 
 	pkg_fragment_free(list);
+	return true;
 }
 
-static void
+static bool
 apply_requires(pkg_t *world, void *unused, int maxdepth, unsigned int flags)
 {
 	pkg_dependency_t *iter;
@@ -316,9 +349,10 @@ apply_requires(pkg_t *world, void *unused, int maxdepth, unsigned int flags)
 
 		pkg_free(pkg);
 	}
+	return true;
 }
 
-static void
+static bool
 apply_requires_private(pkg_t *world, void *unused, int maxdepth, unsigned int flags)
 {
 	pkg_dependency_t *iter;
@@ -334,6 +368,7 @@ apply_requires_private(pkg_t *world, void *unused, int maxdepth, unsigned int fl
 
 		pkg_free(pkg);
 	}
+	return true;
 }
 
 static void
@@ -346,10 +381,17 @@ check_uninstalled(pkg_t *pkg, void *data, unsigned int flags)
 		*retval = EXIT_SUCCESS;
 }
 
-static void
+static bool
 apply_uninstalled(pkg_t *world, void *data, int maxdepth, unsigned int flags)
 {
-	pkg_traverse(world, check_uninstalled, data, maxdepth, flags);
+	int eflag;
+
+	eflag = pkg_traverse(world, check_uninstalled, data, maxdepth, flags);
+
+	if (eflag != PKG_ERRF_OK)
+		return false;
+
+	return true;
 }
 
 static void
@@ -361,10 +403,17 @@ print_graph_node(pkg_t *pkg, void *data, unsigned int flags)
 	printf("Considering graph node '%s' (%p)\n", pkg->id, pkg);
 }
 
-static void
+static bool
 apply_simulate(pkg_t *world, void *data, int maxdepth, unsigned int flags)
 {
-	pkg_traverse(world, print_graph_node, data, maxdepth, flags);
+	int eflag;
+
+	eflag = pkg_traverse(world, print_graph_node, data, maxdepth, flags);
+
+	if (eflag != PKG_ERRF_OK)
+		return false;
+
+	return true;
 }
 
 static void
diff --git a/pkg.c b/pkg.c
index 6d3f270..4d0dc68 100644
--- a/pkg.c
+++ b/pkg.c
@@ -850,7 +850,15 @@ pkg_cflags_collect(pkg_t *pkg, void *data, unsigned int flags)
 pkg_fragment_t *
 pkg_cflags(pkg_t *root, pkg_fragment_t **list, int maxdepth, unsigned int flags)
 {
-	pkg_traverse(root, pkg_cflags_collect, list, maxdepth, flags);
+	int eflag;
+
+	eflag = pkg_traverse(root, pkg_cflags_collect, list, maxdepth, flags);
+
+	if (eflag != PKG_ERRF_OK)
+	{
+		pkg_fragment_free(*list);
+		return NULL;
+	}
 
 	return *list;
 }
@@ -880,10 +888,25 @@ pkg_libs_private_collect(pkg_t *pkg, void *data, unsigned int flags)
 pkg_fragment_t *
 pkg_libs(pkg_t *root, pkg_fragment_t **list, int maxdepth, unsigned int flags)
 {
-	pkg_traverse(root, pkg_libs_collect, list, maxdepth, flags);
+	int eflag;
+
+	eflag = pkg_traverse(root, pkg_libs_collect, list, maxdepth, flags);
+
+	if (eflag != PKG_ERRF_OK)
+	{
+		pkg_fragment_free(*list);
+		return NULL;
+	}
 
 	if (flags & PKGF_MERGE_PRIVATE_FRAGMENTS)
-		pkg_traverse(root, pkg_libs_private_collect, list, maxdepth, flags);
+	{
+		eflag = pkg_traverse(root, pkg_libs_private_collect, list, maxdepth, flags);
+		if (eflag != PKG_ERRF_OK)
+		{
+			pkg_fragment_free(*list);
+			return NULL;
+		}
+	}
 
 	return *list;
 }
diff --git a/pkg.h b/pkg.h
index d548e71..3ddb2d1 100644
--- a/pkg.h
+++ b/pkg.h
@@ -122,7 +122,7 @@ struct pkg_ {
 
 typedef void (*pkg_iteration_func_t)(const pkg_t *pkg);
 typedef void (*pkg_traverse_func_t)(pkg_t *pkg, void *data, unsigned int flags);
-typedef void (*pkg_queue_apply_func_t)(pkg_t *world, void *data, int maxdepth, unsigned int flags);
+typedef bool (*pkg_queue_apply_func_t)(pkg_t *world, void *data, int maxdepth, unsigned int flags);
 
 /* pkg.c */
 void pkg_free(pkg_t *pkg);
diff --git a/queue.c b/queue.c
index abec853..187e61a 100644
--- a/queue.c
+++ b/queue.c
@@ -85,7 +85,11 @@ pkg_queue_apply(pkg_queue_t *head, pkg_queue_apply_func_t func, int maxdepth, un
 	if (pkg_queue_verify(&world, head, maxdepth, flags) != PKG_ERRF_OK)
 		return false;
 
-	func(&world, data, maxdepth, flags);
+	if (!func(&world, data, maxdepth, flags))
+	{
+		pkg_free(&world);
+		return false;
+	}
 
 	pkg_free(&world);
 
diff --git a/tests/lib1/missing-require.pc b/tests/lib1/missing-require.pc
new file mode 100644
index 0000000..d9a5ffb
--- /dev/null
+++ b/tests/lib1/missing-require.pc
@@ -0,0 +1,11 @@
+prefix=/usr
+exec_prefix=${prefix}
+libdir=${prefix}/lib
+includedir=${prefix}/include
+
+Name: missing-require
+Description: A testing pkg-config file
+Version: 1.2.3
+Requires.private: missing
+Libs: -L${libdir} -lfoo
+Cflags: -fPIC -I${includedir}/foo
diff --git a/tests/run.sh.in b/tests/run.sh.in
index eb07410..231af22 100644
--- a/tests/run.sh.in
+++ b/tests/run.sh.in
@@ -163,6 +163,10 @@ run_test "PKG_CONFIG_PATH=${selfdir}/lib1 ${1} --max-version 1.0 'foo '; echo \$
 run_test "PKG_CONFIG_PATH=${selfdir}/lib1 ${1} --max-version 2.0 'foo '; echo \$?" \
 	'0'
 
+# test missing requires
+run_test "PKG_CONFIG_PATH=${selfdir}/lib1 ${1} --cflags missing-require; echo \$?" \
+	'1'
+
 # 10) tests for internal getopt implementation with options at the end
 if [ "x@STRICT_MODE@" = "xno" ]; then
 	run_test "PKG_CONFIG_PATH=${selfdir}/lib1 ${1} foo --libs" \