diff --git a/src/common/rendering/gl/gl_shader.cpp b/src/common/rendering/gl/gl_shader.cpp
index 79612885c..5694b7ef0 100644
--- a/src/common/rendering/gl/gl_shader.cpp
+++ b/src/common/rendering/gl/gl_shader.cpp
@@ -404,7 +404,8 @@ bool FShader::Load(const char * name, const char * vert_prog_lump, const char *
 
 		if (*proc_prog_lump != '#')
 		{
-			int pp_lump = fileSystem.CheckNumForFullName(proc_prog_lump);
+			int pp_lump = fileSystem.CheckNumForFullName(proc_prog_lump, 0);	// if it's a core shader, ignore overrides by user mods.
+			if (pp_lump == -1) pp_lump = fileSystem.CheckNumForFullName(proc_prog_lump);
 			if (pp_lump == -1) I_Error("Unable to load '%s'", proc_prog_lump);
 			FileData pp_data = fileSystem.ReadFile(pp_lump);
 
diff --git a/src/common/rendering/vulkan/shaders/vk_shader.cpp b/src/common/rendering/vulkan/shaders/vk_shader.cpp
index 84f7d3d5e..df065e1ce 100644
--- a/src/common/rendering/vulkan/shaders/vk_shader.cpp
+++ b/src/common/rendering/vulkan/shaders/vk_shader.cpp
@@ -386,7 +386,8 @@ FString VkShaderManager::GetTargetGlslVersion()
 
 FString VkShaderManager::LoadPublicShaderLump(const char *lumpname)
 {
-	int lump = fileSystem.CheckNumForFullName(lumpname);
+	int lump = fileSystem.CheckNumForFullName(lumpname, 0);
+	if (lump == -1) lump = fileSystem.CheckNumForFullName(lumpname);
 	if (lump == -1) I_Error("Unable to load '%s'", lumpname);
 	FileData data = fileSystem.ReadFile(lump);
 	return data.GetString();