diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4f995f33..69a2f5ff 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -64,7 +64,12 @@ option(ISLE_USE_SMARTHEAP "Build LEGO1.DLL with SmartHeap" ${MSVC_FOR_DECOMP})
 option(ISLE_USE_DX5 "Build with internal DirectX 5 SDK" ON)
 option(ISLE_DECOMP_ASSERT "Assert struct size" ${MSVC_FOR_DECOMP})
 cmake_dependent_option(ISLE_USE_DX5_LIBS "Build with internal DirectX 5 SDK Libraries" ON ISLE_USE_DX5 OFF)
-option(ISLE_BUILD_BETA10 "Build BETA10.EXE library" OFF)
+option(ISLE_BUILD_LEGO1 "Build LEGO1.DLL library" ON)
+option(ISLE_BUILD_BETA10 "Build BETA10.DLL library" OFF)
+
+if(NOT (ISLE_BUILD_LEGO1 OR ISLE_BUILD_BETA10))
+  message(FATAL_ERROR "ISLE_BUILD_LEGO1 AND ISLE_BUILD_BETA10 cannot be both disabled")
+endif()
 
 add_cxx_warning(parentheses)
 
@@ -460,14 +465,16 @@ if (ISLE_USE_SMARTHEAP)
   list(APPEND lego1_link_libraries SmartHeap::SmartHeap)
 endif()
 
-add_lego_libraries(lego1
-  LINK_LIBRARIES ${lego1_link_libraries}
-  DLL_OUTPUT_NAME "LEGO1"
-  DLL_PREFIX ""
-  DLL_SUFFIX ".DLL"
-  OUT_TARGETS lego1_targets
-)
-reccmp_add_target(lego1 ID LEGO1)
+if(ISLE_BUILD_LEGO1)
+  add_lego_libraries(lego1
+    LINK_LIBRARIES ${lego1_link_libraries}
+    DLL_OUTPUT_NAME "LEGO1"
+    DLL_PREFIX ""
+    DLL_SUFFIX ".DLL"
+    OUT_TARGETS lego1_targets
+  )
+  reccmp_add_target(lego1 ID LEGO1)
+endif()
 
 if(ISLE_BUILD_BETA10)
   add_lego_libraries(beta10
@@ -478,6 +485,7 @@ if(ISLE_BUILD_BETA10)
     OUT_TARGETS beta10_targets
   )
   reccmp_add_target(beta10 ID BETA10)
+  target_compile_definitions(beta10 PRIVATE BETA10)
 endif()
 
 if (ISLE_BUILD_APP)
@@ -497,7 +505,12 @@ if (ISLE_BUILD_APP)
   endif()
 
   # Link DSOUND, WINMM, and LEGO1
-  target_link_libraries(isle PRIVATE dsound winmm lego1)
+  target_link_libraries(isle PRIVATE dsound winmm)
+  if(ISLE_BUILD_LEGO1)
+    target_link_libraries(isle PRIVATE lego1)
+  else()
+    target_link_libraries(isle PRIVATE beta10)
+  endif()
 
   # Make sure filenames are ALL CAPS
   set_property(TARGET isle PROPERTY OUTPUT_NAME ISLE)
@@ -576,10 +589,11 @@ if (MSVC_FOR_DECOMP)
     set_property(TARGET isle ${lego1_targets} PROPERTY MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
   endif()
 
-  target_link_options(lego1 PRIVATE "/OPT:REF")
-
-  # Equivalent to target_compile_options(... PRIVATE "/MT$<$<CONFIG:Debug>:d>")
-  set_property(TARGET lego1 ${lego1_targets} ${beta10_targets} PROPERTY MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
+  if(TARGET lego1)
+    target_link_options(lego1 PRIVATE "/OPT:REF")
+    # Equivalent to target_compile_options(... PRIVATE "/MT$<$<CONFIG:Debug>:d>")
+    set_property(TARGET lego1 ${lego1_targets} ${beta10_targets} PROPERTY MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
+  endif()
 
   set(CMAKE_CXX_FLAGS "/W3 /GX /D \"WIN32\" /D \"_WINDOWS\"")
   set(CMAKE_CXX_FLAGS_DEBUG "/Gm /Zi /Od /D \"_DEBUG\"")
diff --git a/LEGO1/lego/legoomni/src/actors/act2actor.cpp b/LEGO1/lego/legoomni/src/actors/act2actor.cpp
index a13abf1c..014f03a0 100644
--- a/LEGO1/lego/legoomni/src/actors/act2actor.cpp
+++ b/LEGO1/lego/legoomni/src/actors/act2actor.cpp
@@ -200,7 +200,7 @@ void Act2Actor::Animate(float p_time)
 {
 	int dummy1; // for BETA10, not sure what it is being used for
 
-#ifdef NDEBUG
+#ifndef BETA10
 	MxFloat local48float = 0.0f;
 	if (g_unk0x100f0f1c != 0.0f) {
 		local48float = p_time - g_unk0x100f0f1c;
@@ -221,14 +221,14 @@ void Act2Actor::Animate(float p_time)
 			m_unk0x20 = 0;
 		}
 		else {
-#ifdef NDEBUG
+#ifndef BETA10
 			m_unk0x20 += local48float;
 #endif
 			MxMatrix matrix = m_roi->GetLocal2World();
 			matrix[3][1] += 3.0f;
 			m_roi->UpdateTransformationRelativeToParent(matrix);
 
-#ifdef NDEBUG
+#ifndef BETA10
 			LegoROI* brickstrROI = FindROI("brickstr");
 			MxMatrix brickstrMatrix = brickstrROI->GetLocal2World();
 			brickstrMatrix[3][1] += 3.0f;
@@ -272,7 +272,7 @@ void Act2Actor::Animate(float p_time)
 			CurrentWorld()->RemoveActor(this);
 			return;
 		}
-#ifdef NDEBUG
+#ifndef BETA10
 		else if (m_unk0x1e == 4) {
 			if (m_worldSpeed == 0.0f) {
 				return;
@@ -340,7 +340,7 @@ void Act2Actor::Animate(float p_time)
 									FUN_100199f0(0);
 								}
 								else
-#ifdef NDEBUG
+#ifndef BETA10
 									if (p_time - m_unk0x24 > 3000.0f) {
 #endif
 									SetWorldSpeed(m_unk0x28 - 1);
@@ -350,7 +350,7 @@ void Act2Actor::Animate(float p_time)
 									if (((LegoAct2*) CurrentWorld())->FUN_100516b0() == SUCCESS) {
 										FUN_100199f0(1);
 									}
-#ifdef NDEBUG
+#ifndef BETA10
 								}
 #endif
 							}
diff --git a/LEGO1/lego/legoomni/src/build/legocarbuild.cpp b/LEGO1/lego/legoomni/src/build/legocarbuild.cpp
index 2187a4c2..61f6fc15 100644
--- a/LEGO1/lego/legoomni/src/build/legocarbuild.cpp
+++ b/LEGO1/lego/legoomni/src/build/legocarbuild.cpp
@@ -945,7 +945,7 @@ MxS32 LegoCarBuild::FUN_10024850(MxLong p_x, MxLong p_y)
 	return result;
 }
 
-#ifdef NDEBUG
+#ifndef BETA10
 
 // FUNCTION: LEGO1 0x10024890
 undefined4 LegoCarBuild::FUN_10024890(MxParam* p_param)
@@ -1492,8 +1492,7 @@ void LegoCarBuild::FUN_10025720(undefined4 p_param)
 	m_unk0x10a = 0;
 	MxS32 uVar6;
 
-#ifdef NDEBUG
-
+#ifndef BETA10
 	if (GameState()->GetCurrentAct() == LegoGameState::e_act2) {
 		// This is most likely related to the helicopter rebuild in Act 2
 		switch (p_param) {
@@ -1595,7 +1594,7 @@ void LegoCarBuild::FUN_10025720(undefined4 p_param)
 			assert(m_numAnimsRun >= 0);
 			return;
 		}
-#ifdef NDEBUG
+#ifndef BETA10
 	}
 #endif
 
diff --git a/LEGO1/lego/legoomni/src/build/legocarbuildpresenter.cpp b/LEGO1/lego/legoomni/src/build/legocarbuildpresenter.cpp
index b19fbcc8..2489b1ec 100644
--- a/LEGO1/lego/legoomni/src/build/legocarbuildpresenter.cpp
+++ b/LEGO1/lego/legoomni/src/build/legocarbuildpresenter.cpp
@@ -147,7 +147,7 @@ void LegoCarBuildAnimPresenter::ReadyTickle()
 			return;
 		}
 
-#ifdef NDEBUG
+#ifndef BETA10
 		if (!m_anim) {
 			return;
 		}
diff --git a/LEGO1/lego/legoomni/src/entity/legojetskiraceactor.cpp b/LEGO1/lego/legoomni/src/entity/legojetskiraceactor.cpp
index af3dd04c..a4104078 100644
--- a/LEGO1/lego/legoomni/src/entity/legojetskiraceactor.cpp
+++ b/LEGO1/lego/legoomni/src/entity/legojetskiraceactor.cpp
@@ -100,7 +100,7 @@ MxS32 LegoJetskiRaceActor::VTable0x1c(LegoPathBoundary* p_boundary, LegoEdge* p_
 			}
 
 			if (VTable0x80(m_roi->GetWorldPosition(), worldDirection, a, c)) {
-#ifdef NDEBUG
+#ifndef BETA10
 				m_unk0x7c = 0;
 				return 0;
 #else
diff --git a/LEGO1/lego/legoomni/src/race/legoracespecial.cpp b/LEGO1/lego/legoomni/src/race/legoracespecial.cpp
index e35c943d..d15a561f 100644
--- a/LEGO1/lego/legoomni/src/race/legoracespecial.cpp
+++ b/LEGO1/lego/legoomni/src/race/legoracespecial.cpp
@@ -271,7 +271,7 @@ MxResult LegoCarRaceActor::VTable0x9c()
 
 		MxResult res = VTable0x80(m_roi->GetWorldPosition(), point4, point1, point5);
 
-#ifndef NDEBUG // BETA10 only
+#ifdef BETA10
 		if (res) {
 			assert(0);
 			return -1;