diff --git a/lib/formatter.c b/lib/formatter.c
index 444d5c6..72532fc 100644
--- a/lib/formatter.c
+++ b/lib/formatter.c
@@ -26,7 +26,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <time.h>
 
 #include "udunits2.h"
 #include "unitToIdMap.h"
diff --git a/lib/prefix.h b/lib/prefix.h
index 63b9dc1..5f13cec 100644
--- a/lib/prefix.h
+++ b/lib/prefix.h
@@ -5,6 +5,8 @@
 #ifndef UT_PREFIX_H
 #define UT_PREFIX_H
 
+#include <stddef.h>
+
 #include "udunits2.h"
 
 #ifdef __cplusplus
diff --git a/lib/udunits2.h b/lib/udunits2.h
index 7dcdaac..52b0734 100644
--- a/lib/udunits2.h
+++ b/lib/udunits2.h
@@ -12,10 +12,9 @@
 #include <stddef.h>
 
 #ifdef _MSC_VER
-#include <stdlib.h>
-#include <stdio.h>
-#include <stdarg.h>
 #include <io.h>
+#include <stdio.h>
+#include <stdlib.h>
 
 #define _USE_MATH_DEFINES
 
diff --git a/lib/unitcore.c b/lib/unitcore.c
index de2e058..67e8416 100644
--- a/lib/unitcore.c
+++ b/lib/unitcore.c
@@ -40,35 +40,22 @@
 #endif
 
 #include <assert.h>
-#include <ctype.h>
 #include <errno.h>
 #include <float.h>
-#ifndef _MSC_VER
-#include <inttypes.h>
-#else
-#define int32_t __int32
-#endif
+#include <stdint.h>
 
 #ifdef _MSC_VER
 #define _USE_MATH_DEFINES
 #endif
 
-#include <limits.h>
 #include <math.h>
 
-#ifdef _MSC_VER
-#include "tsearch.h"
-#else
-#include <search.h>
-#endif
-
 #include <stdbool.h>
 #include <stddef.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#ifndef _MSC_VER
 
+#ifndef _MSC_VER
 #include <strings.h>
 #endif
 
diff --git a/lib/xml.c b/lib/xml.c
index 1e86c4c..794eaa7 100644
--- a/lib/xml.c
+++ b/lib/xml.c
@@ -31,6 +31,7 @@
 #include <libgen.h>
 #endif
 #include <limits.h>
+#include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>