diff --git a/libs/vkd3d-shader/hlsl.h b/libs/vkd3d-shader/hlsl.h
index 1d0b3f87..30665fcb 100644
--- a/libs/vkd3d-shader/hlsl.h
+++ b/libs/vkd3d-shader/hlsl.h
@@ -1688,9 +1688,6 @@ struct extern_resource *sm4_get_extern_resources(struct hlsl_ctx *ctx, unsigned
 void sm4_free_extern_resources(struct extern_resource *extern_resources, unsigned int count);
 void sm4_generate_rdef(struct hlsl_ctx *ctx, struct vkd3d_shader_code *rdef);
 
-enum vkd3d_shader_interpolation_mode sm4_get_interpolation_mode(struct hlsl_type *type,
-        unsigned int storage_modifiers);
-
 struct hlsl_ir_function_decl *hlsl_compile_internal_function(struct hlsl_ctx *ctx, const char *name, const char *hlsl);
 
 int hlsl_lexer_compile(struct hlsl_ctx *ctx, const struct vkd3d_shader_code *hlsl);
diff --git a/libs/vkd3d-shader/hlsl_codegen.c b/libs/vkd3d-shader/hlsl_codegen.c
index 08f139f5..f779c261 100644
--- a/libs/vkd3d-shader/hlsl_codegen.c
+++ b/libs/vkd3d-shader/hlsl_codegen.c
@@ -5489,7 +5489,8 @@ static uint32_t allocate_temp_registers(struct hlsl_ctx *ctx, struct hlsl_ir_fun
     return allocator.reg_count;
 }
 
-enum vkd3d_shader_interpolation_mode sm4_get_interpolation_mode(struct hlsl_type *type, unsigned int storage_modifiers)
+static enum vkd3d_shader_interpolation_mode sm4_get_interpolation_mode(struct hlsl_type *type,
+        unsigned int storage_modifiers)
 {
     unsigned int i;