diff -u -r a/src/cmake/externalpackages.cmake b/src/cmake/externalpackages.cmake
--- a/src/cmake/externalpackages.cmake
+++ b/src/cmake/externalpackages.cmake
@@ -193,6 +193,11 @@
 else ()
     set (OpenColorIO_FOUND 0)
 endif ()
+if(USE_OPENCOLORIO AND TARGET Imath::Imath AND OIIO_USING_IMATH STREQUAL "2")
+    message(FATAL_ERROR
+        "OpenColorIO and OpenEXR use incompatible versions of Imath. "
+        "You cannot use openimageio[opencolorio] for this configuration.")
+endif()
 
 set(OPENCV_INCLUDES "")
 set(OPENCV_LIBRARIES opencv_core)