diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2ed1589cfc..79f3612b8b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -216,6 +216,12 @@ if (IGNORE_HOMEBREWED_DEPS)
              )
     endforeach ()
 
+    # Also ignore the whole prefixes, which (unlike CMAKE_IGNORE_PATH) is
+    # honored by config-package searches, and is forwarded to local
+    # dependency child builds so they can't quietly resolve a Homebrew
+    # package (e.g. a mismatched Imath) that we ourselves are ignoring.
+    list (APPEND CMAKE_IGNORE_PREFIX_PATH ${HOMEBREW_PREFIXES})
+
     message (STATUS "CMAKE_IGNORE_PATH: ${CMAKE_IGNORE_PATH}")
 endif ()
 
diff --git a/src/cmake/dependency_utils.cmake b/src/cmake/dependency_utils.cmake
index 25a1172555..79decedde6 100644
--- a/src/cmake/dependency_utils.cmake
+++ b/src/cmake/dependency_utils.cmake
@@ -694,6 +694,10 @@ macro (build_dependency_with_cmake pkgname)
         string(REPLACE ";" "\\;" CMAKE_IGNORE_PATH_ESCAPED "${CMAKE_IGNORE_PATH}")
         list(APPEND _pkg_CMAKE_ARGS "-DCMAKE_IGNORE_PATH=${CMAKE_IGNORE_PATH_ESCAPED}")
     endif()
+    if (CMAKE_IGNORE_PREFIX_PATH)
+        string(REPLACE ";" "\\;" CMAKE_IGNORE_PREFIX_PATH_ESCAPED "${CMAKE_IGNORE_PREFIX_PATH}")
+        list(APPEND _pkg_CMAKE_ARGS "-DCMAKE_IGNORE_PREFIX_PATH=${CMAKE_IGNORE_PREFIX_PATH_ESCAPED}")
+    endif()
 
     # Pass along any CMAKE_MSVC_RUNTIME_LIBRARY
     if (WIN32 AND CMAKE_MSVC_RUNTIME_LIBRARY)