diff --git a/Modules/Platform/AIX.cmake b/Modules/Platform/AIX.cmake
index 58c648319..551a995aa 100644
--- a/Modules/Platform/AIX.cmake
+++ b/Modules/Platform/AIX.cmake
@@ -8,7 +8,9 @@ set(CMAKE_DL_LIBS "-lld")
 # -Wl,-blibpath:/usr/lib:/lib whether RPATH support is on or not.
 # When our own RPATH is to be added it may be inserted before the
 # "always" paths.
-set(CMAKE_PLATFORM_REQUIRED_RUNTIME_PATH /usr/lib /lib)
+if(NOT DEFINED CMAKE_PLATFORM_REQUIRED_RUNTIME_PATH)
+  set(CMAKE_PLATFORM_REQUIRED_RUNTIME_PATH /usr/lib /lib)
+endif()
 
 # Files named "libfoo.a" may actually be shared libraries.
 set_property(GLOBAL PROPERTY TARGET_ARCHIVES_MAY_BE_SHARED_LIBS 1)
diff --git a/Modules/Platform/HP-UX.cmake b/Modules/Platform/HP-UX.cmake
index 88932ad67..9572a7ebb 100644
--- a/Modules/Platform/HP-UX.cmake
+++ b/Modules/Platform/HP-UX.cmake
@@ -1,4 +1,6 @@
-set(CMAKE_PLATFORM_REQUIRED_RUNTIME_PATH /usr/lib)
+if(NOT DEFINED CMAKE_PLATFORM_REQUIRED_RUNTIME_PATH)
+  set(CMAKE_PLATFORM_REQUIRED_RUNTIME_PATH /usr/lib)
+endif()
 
 if(NOT CMAKE_SYSTEM_PROCESSOR STREQUAL "ia64")
   set(CMAKE_SHARED_LIBRARY_SUFFIX ".sl")          # .so