diff --git a/hw/xbox/nv2a/pgraph/glsl/vsh.c b/hw/xbox/nv2a/pgraph/glsl/vsh.c
index b6b7045186..bf4a14e23e 100644
--- a/hw/xbox/nv2a/pgraph/glsl/vsh.c
+++ b/hw/xbox/nv2a/pgraph/glsl/vsh.c
@@ -53,6 +53,8 @@ MString *pgraph_gen_vsh_glsl(const ShaderState *state, bool prefix_outputs)
         GLSL_DEFINE(texMat2, GLSL_C_MAT4(NV_IGRAPH_XF_XFCTX_T2MAT))
         GLSL_DEFINE(texMat3, GLSL_C_MAT4(NV_IGRAPH_XF_XFCTX_T3MAT))
 
+        "\n"
+        "#define FLOAT_MAX uintBitsToFloat(0x7F7FFFFFu)\n"
         "\n"
         "vec4 oPos = vec4(0.0,0.0,0.0,1.0);\n"
         "vec4 oD0 = vec4(0.0,0.0,0.0,1.0);\n"
@@ -244,7 +246,13 @@ MString *pgraph_gen_vsh_glsl(const ShaderState *state, bool prefix_outputs)
             break;
         }
 
-        mstring_append(body, "  oFog = NaNToOne(vec4(fogFactor));\n");
+        /* Fog is clamped to min/max normal float values here to match HW
+         * interpolation. It is then clamped to [0,1] in the pixel shader.
+         */
+        // clang-format off
+        mstring_append(body,
+                       "  oFog = clamp(NaNToOne(vec4(fogFactor)), -FLOAT_MAX, FLOAT_MAX);\n");
+        // clang-format on
     } else {
         /* FIXME: Is the fog still calculated / passed somehow?!
          */