diff --git a/libs/vkd3d-shader/d3dbc.c b/libs/vkd3d-shader/d3dbc.c
index 7e0eac6c..3d139416 100644
--- a/libs/vkd3d-shader/d3dbc.c
+++ b/libs/vkd3d-shader/d3dbc.c
@@ -855,6 +855,14 @@ static void shader_sm1_skip_opcode(const struct vkd3d_shader_sm1_parser *sm1, co
     {
         *ptr += 2;
     }
+    /* Somewhat similarly, DEF and DEFI have a single source, but need to read
+     * four tokens for that source. See shader_sm1_read_immconst().
+     * Technically shader model 1 doesn't have integer registers or DEFI; we
+     * handle it here anyway because it's easy. */
+    else if (opcode_info->vkd3d_opcode == VKD3DSIH_DEF || opcode_info->vkd3d_opcode == VKD3DSIH_DEFI)
+    {
+        *ptr += 3;
+    }
 
     *ptr += (opcode_info->dst_count + opcode_info->src_count);
 }
diff --git a/tests/vkd3d_shader_api.c b/tests/vkd3d_shader_api.c
index 9fe5eec8..61c412c5 100644
--- a/tests/vkd3d_shader_api.c
+++ b/tests/vkd3d_shader_api.c
@@ -238,6 +238,13 @@ static void test_d3dbc(void)
         0xfffe0100, /* vs_1_0 */
         0x0000ffff, /* end */
     };
+    static const uint32_t vs_dcl_def[] =
+    {
+        0xfffe0101,                                                             /* vs_1_1 */
+        0x0000001f, 0x80000000, 0x900f0000,                                     /* dcl_position v0  */
+        0x00000051, 0xa00f0000, 0x3f800000, 0x00000000, 0x00000000, 0x3f800000, /* def c0, 1.0, 0.0, 0.0, 1.0   */
+        0x0000ffff,                                                             /* end */
+    };
     static const uint32_t invalid_type[] =
     {
         0x00010100, /* <invalid>_1_0 */
@@ -255,6 +262,10 @@ static void test_d3dbc(void)
         0x0000ffff,                         /* end */
     };
     static const char expected[] = "vs_1_0\n";
+    static const char expected_dcl_def[] =
+        "vs_1_1\n"
+        "dcl_position0 v0\n"
+        "def c0 = 1.00000000e+00, 0.00000000e+00, 0.00000000e+00, 1.00000000e+00\n";
 
     info.type = VKD3D_SHADER_STRUCTURE_TYPE_COMPILE_INFO;
     info.next = NULL;
@@ -291,6 +302,15 @@ static void test_d3dbc(void)
     rc = vkd3d_shader_compile(&info, &d3d_asm, NULL);
     ok(rc == VKD3D_ERROR_INVALID_SHADER, "Got unexpected error code %d.\n", rc);
 
+    info.source.code = vs_dcl_def;
+    info.source.size = sizeof(vs_dcl_def);
+    rc = vkd3d_shader_compile(&info, &d3d_asm, NULL);
+    ok(rc == VKD3D_OK, "Got unexpected error code %d.\n", rc);
+    ok(d3d_asm.size == strlen(expected_dcl_def), "Got unexpected size %zu.\n", d3d_asm.size);
+    ok(!memcmp(d3d_asm.code, expected_dcl_def, d3d_asm.size), "Got unexpected code \"%.*s\"\n",
+            (int)d3d_asm.size, (char *)d3d_asm.code);
+    vkd3d_shader_free_shader_code(&d3d_asm);
+
     info.source.code = invalid_type;
     info.source.size = sizeof(invalid_type);
     rc = vkd3d_shader_compile(&info, &d3d_asm, NULL);