diff --git a/contrib/zopfli/CMakeLists.txt b/contrib/zopfli/CMakeLists.txt
index 995ffc1..d9b187f 100644
--- a/contrib/zopfli/CMakeLists.txt
+++ b/contrib/zopfli/CMakeLists.txt
@@ -48,9 +48,9 @@ add_sapi_library(
 
     ZopfliCompressFD
   INPUTS
-    ${zopfli_SOURCE_DIR}/src/zopfli/deflate.h
-    ${zopfli_SOURCE_DIR}/src/zopfli/gzip_container.h
-    ${zopfli_SOURCE_DIR}/src/zopfli/zlib_container.h
+    "${zopfli_SOURCE_DIR}/src/zopfli/deflate.h"
+    "${zopfli_SOURCE_DIR}/src/zopfli/gzip_container.h"
+    "${zopfli_SOURCE_DIR}/src/zopfli/zlib_container.h"
     wrapper/wrapper_zopfli.h
 
   LIBRARY wrapper_zopfli
diff --git a/contrib/zstd/CMakeLists.txt b/contrib/zstd/CMakeLists.txt
index 0062e49..8444240 100644
--- a/contrib/zstd/CMakeLists.txt
+++ b/contrib/zstd/CMakeLists.txt
@@ -78,7 +78,7 @@ add_sapi_library(
     ZSTD_decompress_fd
     ZSTD_decompressStream_fd
   INPUTS
-    ${libzstd_INCLUDE_DIR}/zstd.h
+    "${libzstd_INCLUDE_DIR}/zstd.h"
     wrapper/wrapper_zstd.h
 
   LIBRARY wrapper_zstd