diff --git a/src/lib/icu/CaseFold.cxx b/src/lib/icu/CaseFold.cxx
index 26ae6cba5..d41240c30 100644
--- a/src/lib/icu/CaseFold.cxx
+++ b/src/lib/icu/CaseFold.cxx
@@ -32,7 +32,6 @@
 #include <unicode/ustring.h>
 #else
 #include <algorithm>
-#include <ctype.h>
 #endif
 
 #ifdef _WIN32
diff --git a/src/lib/icu/Collate.cxx b/src/lib/icu/Collate.cxx
index d3cf68cb1..ee1bb8f88 100644
--- a/src/lib/icu/Collate.cxx
+++ b/src/lib/icu/Collate.cxx
@@ -29,7 +29,6 @@
 #include <unicode/ustring.h>
 #else
 #include <algorithm>
-#include <ctype.h>
 #endif
 
 #ifdef _WIN32
diff --git a/src/output/plugins/OSXOutputPlugin.cxx b/src/output/plugins/OSXOutputPlugin.cxx
index 90946bb9f..312d16965 100644
--- a/src/output/plugins/OSXOutputPlugin.cxx
+++ b/src/output/plugins/OSXOutputPlugin.cxx
@@ -266,7 +266,7 @@ osx_output_parse_channel_map(const char *device_name,
 		}
 
 		if (want_number &&
-			(isdigit(*channel_map_str) || *channel_map_str == '-')
+			(std::isdigit(*channel_map_str) || *channel_map_str == '-')
 		) {
 			channel_map[inserted_channels] = strtol(channel_map_str, &endptr, 10);
 			if (channel_map[inserted_channels] < -1)