diff --git a/src/rendering/vulkan/renderer/vk_postprocess.cpp b/src/rendering/vulkan/renderer/vk_postprocess.cpp
index 5ebb03c9a..38cd442c7 100644
--- a/src/rendering/vulkan/renderer/vk_postprocess.cpp
+++ b/src/rendering/vulkan/renderer/vk_postprocess.cpp
@@ -216,7 +216,7 @@ void VkPostprocess::CompileEffectShaders()
 FString VkPostprocess::LoadShaderCode(const FString &lumpName, const FString &defines, int version)
 {
 	int lump = Wads.CheckNumForFullName(lumpName, 0);
-	if (lump == -1) I_FatalError("Unable to load '%s'", lumpName);
+	if (lump == -1) I_FatalError("Unable to load '%s'", lumpName.GetChars());
 	FString code = Wads.ReadLump(lump).GetString().GetChars();
 
 	FString patchedCode;