diff --git a/cmake/modules/FindUnuran.cmake b/cmake/modules/FindUnuran.cmake
index a704769c23769f66478414626a50b0a21494ac7f..a4b08773219a692fc84d2613bfc8568734406e5b 100644
--- a/cmake/modules/FindUnuran.cmake
+++ b/cmake/modules/FindUnuran.cmake
@@ -10,7 +10,9 @@ find_path(UNURAN_INCLUDE_DIR NAMES unuran.h HINTS ${UNURAN_DIR}/include $ENV{UNU
 find_library(UNURAN_LIBRARY NAMES unuran HINTS ${UNURAN_DIR}/lib $ENV{UNURAN_DIR}/lib)
 
 set(UNURAN_INCLUDE_DIRS ${UNURAN_INCLUDE_DIR})
-set(UNURAN_LIBRARIES ${UNURAN_LIBRARY})
+if(UNURAN_LIBRARY)
+  set(UNURAN_LIBRARIES ${UNURAN_LIBRARY})
+endif()
 
 
 # handle the QUIETLY and REQUIRED arguments and set UNURAN_FOUND to TRUE if