diff --git a/config/cmake/ConfigureChecks.cmake b/config/cmake/ConfigureChecks.cmake
index 120387895a..df3a7bdae3 100644
--- a/config/cmake/ConfigureChecks.cmake
+++ b/config/cmake/ConfigureChecks.cmake
@@ -149,11 +149,13 @@ endif (NOT WINDOWS)
 #-----------------------------------------------------------------------------
 # Check if C has __float128 extension
 #-----------------------------------------------------------------------------
+
 CHECK_TYPE_SIZE("__float128" SIZEOF___FLOAT128)
 if(${HAVE_SIZEOF___FLOAT128})
   SET(H5_HAVE_FLOAT128 1)
 else (${HAVE_SIZEOF___FLOAT128})
   SET(H5_HAVE_FLOAT128 0)
+  SET(SIZEOF___FLOAT128 0)
 endif(${HAVE_SIZEOF___FLOAT128})
 
 #-----------------------------------------------------------------------------