diff --git a/libs/vkd3d-shader/hlsl.y b/libs/vkd3d-shader/hlsl.y
index 4b3ca8c9..3b5915a1 100644
--- a/libs/vkd3d-shader/hlsl.y
+++ b/libs/vkd3d-shader/hlsl.y
@@ -1235,8 +1235,20 @@ static bool parse_reservation_index(struct hlsl_ctx *ctx, const char *string, un
 
     reservation->reg_index = strtoul(string + 1, &endptr, 10) + bracket_offset;
 
-    if (endptr == string + 1)
-        return false;
+    if (*endptr)
+    {
+        /* fxc for SM >= 4 treats all parse failures for 'b' types as successes,
+         * setting index to -1. It will later fail while validating slot limits. */
+        if (reservation->reg_type == 'b' && hlsl_version_ge(ctx, 4, 0))
+        {
+            reservation->reg_index = -1;
+            return true;
+        }
+
+        /* All other types tolerate leftover characters. */
+        if (endptr == string + 1)
+            return false;
+    }
 
     return true;
 }
diff --git a/tests/hlsl/register-reservations-numeric.shader_test b/tests/hlsl/register-reservations-numeric.shader_test
index a6d7e087..f5cb5f24 100644
--- a/tests/hlsl/register-reservations-numeric.shader_test
+++ b/tests/hlsl/register-reservations-numeric.shader_test
@@ -377,7 +377,7 @@ probe (0, 0) rgba (1.0, 1.0, 1.0, 1.0)
 % Weird FXC behavior.
 % SM4 accepts anything for 'b' reservations and discards it silently for global numeric variables.
 
-[pixel shader fail(sm<4 | sm>=6) todo(sm>=4)]
+[pixel shader fail(sm<4 | sm>=6)]
 float a : register(banana);
 
 float4 main() : sv_target
@@ -387,7 +387,7 @@ float4 main() : sv_target
 
 [test]
 uniform 0 float 1.0
-todo(glsl | sm>=4 | sm<6) draw quad
+todo(glsl) draw quad
 probe (0, 0) rgba(1.0, 1.0, 1.0, 1.0)
 
 % Testing other reservation types. This is a parse failure, i.e "X3530: register sa not valid"
@@ -451,7 +451,7 @@ float4 main() : sv_target
 
 % DXC fails during parsing.
 
-[pixel shader fail]
+[pixel shader fail todo]
 cbuffer buf : register(banana)
 {
     float a;