diff --git a/common/popl.hpp b/common/popl.hpp
index f442b514..91f35c52 100644
--- a/common/popl.hpp
+++ b/common/popl.hpp
@@ -33,6 +33,9 @@
 #include <sstream>
 #include <stdexcept>
 #include <vector>
+#ifdef WINDOWS
+#include <cctype>
+#endif
 
 
 namespace popl
diff --git a/common/utils/string_utils.hpp b/common/utils/string_utils.hpp
index 5bd01f98..03428702 100644
--- a/common/utils/string_utils.hpp
+++ b/common/utils/string_utils.hpp
@@ -24,6 +24,9 @@
 #include <stdio.h>
 #include <string>
 #include <vector>
+#ifdef WINDOWS
+#include <cctype>
+#endif
 
 namespace utils
 {
diff --git a/doc/build.md b/doc/build.md
index d84d43ab..f6b39542 100644
--- a/doc/build.md
+++ b/doc/build.md
@@ -314,7 +314,7 @@ This example will show you how to add snapcast to [Buildroot](https://buildroot.
 Prerequisites:
 
  * CMake 
- * Visual Studio 2019 with C++
+ * Visual Studio 2017 or 2019 with C++
 
 Set up [vcpkg](https://github.com/Microsoft/vcpkg)