diff --git a/pkgs/development/libraries/wt/default.nix b/pkgs/development/libraries/wt/default.nix
index 4461975402b..e25b23e84ed 100644
--- a/pkgs/development/libraries/wt/default.nix
+++ b/pkgs/development/libraries/wt/default.nix
@@ -23,7 +23,7 @@ stdenv.mkDerivation rec {
     "-DWT_WRASTERIMAGE_IMPLEMENTATION=GraphicsMagick"
     "-DWT_CPP_11_MODE=-std=c++11"
     "-DGM_PREFIX=${graphicsmagick}"
-    "-DMYSQL_PREFIX=${libmysql}"
+    "-DMYSQL_PREFIX=${libmysql.dev}"
     "--no-warn-unused-cli"
   ];
 
diff --git a/pkgs/tools/backup/bareos/default.nix b/pkgs/tools/backup/bareos/default.nix
index cf44d0e9c26..79da3f8cf9b 100644
--- a/pkgs/tools/backup/bareos/default.nix
+++ b/pkgs/tools/backup/bareos/default.nix
@@ -55,7 +55,7 @@ stdenv.mkDerivation rec {
     ++ optional (openssl != null) "--with-openssl=${openssl.dev}"
     ++ optional (sqlite != null) "--with-sqlite3=${sqlite.dev}"
     ++ optional (postgresql != null) "--with-postgresql=${postgresql}"
-    ++ optional (libmysql != null) "--with-mysql=${libmysql}"
+    ++ optional (libmysql != null) "--with-mysql=${libmysql.dev}"
     ++ optional (zlib != null) "--with-zlib=${zlib.dev}"
     ++ optional (lzo != null) "--with-lzo=${lzo}"
     ++ optional (jansson != null) "--with-jansson=${jansson}"