diff --git a/src/cmake/cuda_macros.cmake b/src/cmake/cuda_macros.cmake
index ca3230e48..c15aa1246 100644
--- a/src/cmake/cuda_macros.cmake
+++ b/src/cmake/cuda_macros.cmake
@@ -20,7 +20,7 @@ function ( NVCC_COMPILE cuda_src ptx_generated extra_nvcc_args )
             "-I${PROJECT_SOURCE_DIR}/src/include"
             "-I${PROJECT_SOURCE_DIR}/src/cuda_common"
             "-I${OPENIMAGEIO_INCLUDES}"
-            "-I${ILMBASE_INCLUDES}"
+            "-I${IMATH_INCLUDES}"
             "-I${Boost_INCLUDE_DIRS}"
             "-DFMT_DEPRECATED=\"\""
             ${LLVM_COMPILE_FLAGS}
diff --git a/src/cmake/externalpackages.cmake b/src/cmake/externalpackages.cmake
index 12b09a393..fb659598f 100644
--- a/src/cmake/externalpackages.cmake
+++ b/src/cmake/externalpackages.cmake
@@ -89,6 +89,12 @@ checked_find_package (OpenEXR REQUIRED
                         "OpenEXR 2.2 is the oldest version our CI tests against, and the minimum that supports DWA compression"
                       PRINT IMATH_INCLUDES
                      )
+# Force Imath includes to be before everything else to ensure that we have
+# the right Imath/OpenEXR version, not some older version in the system
+# library. This shoudn't be necessary, except for the common case of people
+# building against Imath/OpenEXR 3.x when there is still a system-level
+# install version of 2.x.
+include_directories(BEFORE ${IMATH_INCLUDES})
 if (CMAKE_COMPILER_IS_CLANG AND OPENEXR_VERSION VERSION_LESS 2.3)
     # clang C++ >= 11 doesn't like 'register' keyword in old exr headers
     add_compile_options (-Wno-deprecated-register)
diff --git a/src/liboslexec/CMakeLists.txt b/src/liboslexec/CMakeLists.txt
index eb12231cb..79c722f41 100644
--- a/src/liboslexec/CMakeLists.txt
+++ b/src/liboslexec/CMakeLists.txt
@@ -187,7 +187,7 @@ target_include_directories (${local_lib}
     PUBLIC
         ${CMAKE_INSTALL_FULL_INCLUDEDIR}
         ${OPENIMAGEIO_INCLUDES}
-        ${ILMBASE_INCLUDES}
+        ${IMATH_INCLUDES}
     PRIVATE
         "${CMAKE_SOURCE_DIR}/src/liboslcomp"
     )
diff --git a/src/liboslquery/CMakeLists.txt b/src/liboslquery/CMakeLists.txt
index d94ff69fe..ee9959bb7 100644
--- a/src/liboslquery/CMakeLists.txt
+++ b/src/liboslquery/CMakeLists.txt
@@ -13,12 +13,12 @@ target_include_directories (${local_lib}
     PUBLIC
         ${CMAKE_INSTALL_FULL_INCLUDEDIR}
         ${OPENIMAGEIO_INCLUDES}
-        ${ILMBASE_INCLUDES}
+        ${IMATH_INCLUDES}
     PRIVATE
         ../liboslexec)
 target_link_libraries (${local_lib}
     PUBLIC
-        ${OPENIMAGEIO_LIBRARIES} ${ILMBASE_LIBRARIES}
+        ${OPENIMAGEIO_LIBRARIES} ${IMATH_LIBRARIES}
     PRIVATE
         ${Boost_LIBRARIES}
     )