diff --git a/dlls/d3d9/device.c b/dlls/d3d9/device.c
index 9fc49ea3786..dd7f46ada2b 100644
--- a/dlls/d3d9/device.c
+++ b/dlls/d3d9/device.c
@@ -3189,7 +3189,7 @@ static HRESULT WINAPI d3d9_device_GetPixelShaderConstantB(IDirect3DDevice9Ex *if
     TRACE("iface %p, reg_idx %u, data %p, count %u.\n", iface, reg_idx, data, count);
 
     wined3d_mutex_lock();
-    hr = wined3d_device_get_ps_consts_b(device->wined3d_device, reg_idx, data, count);
+    hr = wined3d_device_get_ps_consts_b(device->wined3d_device, reg_idx, count, data);
     wined3d_mutex_unlock();
 
     return hr;
diff --git a/dlls/wined3d/device.c b/dlls/wined3d/device.c
index 43ae2eb9e28..da83b56f140 100644
--- a/dlls/wined3d/device.c
+++ b/dlls/wined3d/device.c
@@ -2640,17 +2640,17 @@ HRESULT CDECL wined3d_device_set_ps_consts_b(struct wined3d_device *device,
 }
 
 HRESULT CDECL wined3d_device_get_ps_consts_b(const struct wined3d_device *device,
-        UINT start_register, BOOL *constants, UINT bool_count)
+        unsigned int start_idx, unsigned int count, BOOL *constants)
 {
-    UINT count = min(bool_count, WINED3D_MAX_CONSTS_B - start_register);
+    TRACE("device %p, start_idx %u, count %u,constants %p.\n",
+            device, start_idx, count, constants);
 
-    TRACE("device %p, start_register %u, constants %p, bool_count %u.\n",
-            device, start_register, constants, bool_count);
-
-    if (!constants || start_register >= WINED3D_MAX_CONSTS_B)
+    if (!constants || start_idx >= WINED3D_MAX_CONSTS_B)
         return WINED3DERR_INVALIDCALL;
 
-    memcpy(constants, &device->state.ps_consts_b[start_register], count * sizeof(BOOL));
+    if (count > WINED3D_MAX_CONSTS_B - start_idx)
+        count = WINED3D_MAX_CONSTS_B - start_idx;
+    memcpy(constants, &device->state.ps_consts_b[start_idx], count * sizeof(*constants));
 
     return WINED3D_OK;
 }
diff --git a/dlls/wined3d/wined3d.spec b/dlls/wined3d/wined3d.spec
index 3d6a641514b..01699dfc4b6 100644
--- a/dlls/wined3d/wined3d.spec
+++ b/dlls/wined3d/wined3d.spec
@@ -70,7 +70,7 @@
 @ cdecl wined3d_device_get_predication(ptr ptr)
 @ cdecl wined3d_device_get_primitive_type(ptr ptr)
 @ cdecl wined3d_device_get_ps_cb(ptr long)
-@ cdecl wined3d_device_get_ps_consts_b(ptr long ptr long)
+@ cdecl wined3d_device_get_ps_consts_b(ptr long long ptr)
 @ cdecl wined3d_device_get_ps_consts_f(ptr long long ptr)
 @ cdecl wined3d_device_get_ps_consts_i(ptr long long ptr)
 @ cdecl wined3d_device_get_ps_resource_view(ptr long)
diff --git a/include/wine/wined3d.h b/include/wine/wined3d.h
index 63550a1c807..a770d7fe95e 100644
--- a/include/wine/wined3d.h
+++ b/include/wine/wined3d.h
@@ -2123,7 +2123,7 @@ void __cdecl wined3d_device_get_primitive_type(const struct wined3d_device *devi
         enum wined3d_primitive_type *primitive_topology);
 struct wined3d_buffer * __cdecl wined3d_device_get_ps_cb(const struct wined3d_device *device, UINT idx);
 HRESULT __cdecl wined3d_device_get_ps_consts_b(const struct wined3d_device *device,
-        UINT start_register, BOOL *constants, UINT bool_count);
+        unsigned int start_idx, unsigned int count, BOOL *constants);
 HRESULT __cdecl wined3d_device_get_ps_consts_f(const struct wined3d_device *device,
         unsigned int start_idx, unsigned int count, struct wined3d_vec4 *constants);
 HRESULT __cdecl wined3d_device_get_ps_consts_i(const struct wined3d_device *device,